There are few, if any, viruses in the wild that affect Mac OS X -- but it's not a bad idea to check attachments and downloads anyway, particularly if you share files with Windows users. ClamXav lets you do just that.
ClamXav is a Mac OS X front-end to ClamAV, probably the most popular anti-virus open source engine. Using ClamXav you can conveniently perform scans for viruses, configure filters, and schedule virus definition updates. The ClamXav Sentry feature allows you to set up background scanning by simply adding folders to its watch list. Once the Sentry is activated, it will quietly scan any file created in these folders.
Growl is a system that makes it possible for Growl-aware applications to send notifications. This allows you, for example, to keep an eye on downloads, new RSS articles, and iTunes tracks without leaving the application you're working in.
With Growl's preference panel you can configure the appearance and behavior of notifications. Once installed and configured, Growl requires virtually no maintenance. When you launch a newly installed Growl-aware application, it registers automatically with Growl, and uses it to send notifications.
Seashore is an effort to build a Mac OS X native graphics application based on the GIMP. Although the application is still in a very early stage of development, it can already be used for some light image manipulation.
Seashore supports channels, gradients, textures, and anti-aliasing for both text and brush strokes. It also features a selection of tools including Paint, Pencil, Smudge, Crop, Text, Eraser, and Color Sampling. More importantly, it uses the GIMP's native .xcf format and sports a GUI similar to GIMP, so users familiar with GIMP will feel at home with Seashore.
If you want to design icons or pixel art, Pixen is the way to go. The package contains some powerful tools, making the drawing process not only easier, but also fun. Besides the usual tools such as eye-dropper, pencil, and eraser, Pixen offers a few unique features, including layers, smart palettes, and tile editor. If you've never tried to create your own icons or pixel art, give Pixen a try.
Vienna is a must-have application for all RSS-addicted Mac users. Vienna is a RSS/Atom reader with a simple user interface. Using Vienna you can easily subscribe to RSS and Atom feeds and manage them. Since the application can import and export feeds using OPML, migrating to Vienna is a pain-free process.
The application includes a feature similar to iTunes' Smart Folders, which allows you to sort articles based on user-defined criteria. For example, you can create a folder containing news articles posted by a certain author or filed under a certain topic. You can also perform searches in the currently selected feed and flag interesting articles. Vienna supports Growl, so you can keep an eye on your favourite RSS feeds even when Vienna is in the background.
Adium X is a slick application that will take care of all your instant messaging needs. Adium supports most common IM protocols, including AOL Instant Messenger, ICQ, Jabber, MSN Messenger, and Yahoo! Messenger as well as more exotic ones such as Gadu-Gadu, Novell Groupwise, and Lotus Sametime.
Adium's message display is based on WebKit, the Apple technology that also powers the Safari Web browser. This makes Adium "themable," and you can change its appearance using HTML and CSS. If you don't want to do it yourself, Adium's Extras Web site offers ready-to-use styles.
If you chat to several people simultaneously, you'll appreciate Adium's tabbed messaging feature, where a single window can contain several conversations in separate tabs. Adium also features Off-the-Record Messaging, which supports encryption and authentication. This allows you to conduct secure, private conversations over IM with other Adium users, as well as users of Gaim on Linux and Windows.
Need a full-featured FTP client? Look no further than Cyberduck. The application contains almost all the features you'll ever need, including support for multiple connections and encodings, bookmarks, resumable downloads, folder synchronisation, and much more.
Cyberduck makes transferring files easy with bookmarks. Create a bookmark for a remote host, and then drag a file to the bookmark for Cyberduck to upload the file. If you use more than one Mac, you can synchronise your bookmarks with .Mac iDisk. Cyberduck supports Growl, AppleScripts, and Bonjour zero-configuration networking. Cyberduck also handles FTP over SSL and FTP over SSH (SFTP), and works with popular external editors like BBEdit, TextWrangler, and SubEthaEdit.
DTV is described as "Internet TV for your Mac." It offers an easy way to subscribe to video channels as well as view videos and manage your collections. DTV acts as a regular RSS reader, but instead of conventional RSS text feeds, you can use it to add videocasts.
Since DTV looks and acts pretty much like Apple's iTunes, Mac users should find it easy to use. When you add a new channel, DTV displays a list of available articles with accompanying videos. Click on the video you want, and DTV will download it for your viewing pleasure. By default, all videos expire after a certain period of time, but you can choose to keep videos in your collection.
If you have trouble finding some good videocasts, your can try the built-in Channel Guide. (ScreenCastsOnline and macTV are the top videocasts for Mac aficionados.) Participatory Culture Foundation, which is responsible for the development of DTV, also offers Broadcast Machine, an application that allows you to create your own videocasts.
Smultron's side pane makes it easy to manage multiple documents and switch between them. Smultron also includes powerful search capabilities -- the quick search tool allows you to quickly find a text string in the open text file, while the Advanced Find supports regular expressions and can be used to perform searches in multiple documents.
Using Smultron you can store reusable blocks of text in a code snippets drawer. To create a new snippet, select the piece of text you want and drag it onto the Smultron drawer. You can even perform searches in the existing snippets.
Smultron also supports different text encodings, .Mac sync of your preferences, and a command-line utility.
OSXvnc and Chicken of the VNC
Chicken of the VNC is a Virtual Network Computing (VNC) client for the Mac. Besides its cute icon and funny name, Chicken of the VNC includes a powerful Profiles feature that can be used to group multiple connections and manage their settings. For example, you can have one profile that contains connections to machines on your local network, and another profile that includes connections to remote computers. Each profile may have its own optimised settings.
OSXvnc is a full-featured VNC server for Mac OS X. One of OSXvnc's most exciting features is support for Mac OS X "Tiger" multiple desktop sessions. Multiple users can be logged into the same Mac, with one user at the computer and another user accessing their desktop remotely using OSXvnc.
You can specify the port OSXvnc listens on, the way it handles incoming connections, its compression encoding, and more.
AppleJack and Preferential Treatment
Although AppleJack is a command-line tool, it's easy to use. Restart your Mac in the single-user mode (Hold down the Command+S key during startup), type
applejack, and you'll see a list of the tasks AppleJack can perform, which includes repairing the hard disk, repairing permissions, validating the system's preference files, and deleting corrupted cache files.
The Preferential Treatment tool allows you to check the user's and system's preference files for corruption by using the plutil command-line tool. When the check is complete you will see a list of files that the application considers damaged. You can then either open and repair them manually or move them to Trash.
This is just a small sample of the open source applications that are available for Mac OS X. Mac users have a wide variety of open source applications to choose from. If your favourite application isn't already there, tell us about it with a comment below.