One of the applications many users ask about when migrating to Linux is Evernote. While the folks at Evernote haven't created a Linux port, you'll find plenty of apps for note taking, organization, and wrangling important personal and business documents.
Some Linux users object to Evernote because it's not open source, but that's only half the problem. Even if you're not picky about software licensing, Evernote isn't an option on Linux. You can run the Evernote plugin on Firefox and Chrome, or you might get lucky running Evernote in Wine. But a native client? Nope. But it is possible to find quite a few free and open source alternatives that provide much of the same functionality.
Tomboy is a simple and effective system for note-taking and storing all those snippets of information that need to go somewhere. It's cross-platform, so you can work with Tomboy on Linux, Mac OS X, and Windows. And since Tomboy saves automatically as you work, it's entirely hassle-free.
Actually, Tomboy has a few up on Evernote. Tomboy works sort of like a desktop wiki and allows you to link notes to one another, and has a plug-in system with a fair number of extensions to add features you might want. Naturally, Tomboy also has good search capabilities. Finding that note from six weeks ago about the infomercial is a snap, so long as you can remember at least part of the note. Tomboy doesn't have search by date, unfortunately, but it does have a timestamp add-in that you can use to tag each note with the date it was created (or updated).
If you're up for hosting your own server, you can even use Snowy to edit, view, sync, and share your Tomboy notes online. Unlike Evernote, with Snowy you have full control over your data. Where Tomboy falls down is that it doesn't store files, just notes. If you want to save those presentations or a PDF with travel info, Tomboy isn't going to be much help. For sharing files between computers, you want to take a look at Dropbox.
Tomboy is installed by default on Ubuntu, Linux Mint, and openSUSE (with the GNOME desktop). Tomboy is in the Fedora repositories, but Fedora ships with a workalike program rather than Tomboy itself.
Dropbox is a simple little application that watches a folder on your system and syncs the files in the folder with storage hosted on Amazon Simple Storage Service (S3). Basic accounts with 2GB of storage are free, and the company offers storage upgrades to 50GB and 100GB. But wait, there's more!
Dropbox also syncs files between computers. If you have a Dropbox account and two computers, it will keep the files synced between them. If you copy a picture to your Dropbox folder, it'll be synced to your other system. If you delete a file, it'll be removed from the other computer, etc. Dropbox has a local LAN feature that allows two (or more) computers running Dropbox to sync files via the LAN without having to be synced up to S3 first. This means that, effectively, any file placed in the Dropbox folder is going to be available on any computer on the local network within seconds or minutes, depending on the size of the file.
In addition, Dropbox has a sharing feature and a public folder. If you want to share files with someone else that's too large to email, just plonk it in Dropbox and create a public link.
Linux support is excellent with Dropbox. Packages are available for Fedora and Ubuntu, and the company also makes source available for the Nautilus plugin so users on other distros can compile Dropbox themselves. Dropbox is not entirely open source, though. You'll also be able to get Dropbox for Windows, Mac OS X, and the iPhone, iPad, Android, and Blackberry support is listed as "coming soon."
Not only does Dropbox help solve the problem of syncing files between computers, it also acts as a backup service. Keep your work documents in Dropbox, and they're automatically backed up "to the cloud." Dropbox even keeps a history of files for up to 30 days, so you can easily restore earlier file revisions or files that are accidentally deleted if you notice soon enough. (They also have an add-on package that extends the storage of revised/deleted files.) I keep pretty much all of my writing, presentations, and other work-related documents in Dropbox and it's made life a great deal simpler.
Since Dropbox is non-free software, there's an effort afoot called SparkleShare as a Dropbox replacement. It's not mature enough to recommend yet — the first version hasn't even been released — but it's worth keeping an eye on.
If you only use one computer, Zim might be a better option than Tomboy. Zim is described as a desktop wiki and has a few features that you won't find in Tomboy — namely, the ability to attach files to notes, a task plugin, and other goodies.
Like Tomboy, Zim is good for taking notes on the fly or for more structured content. You can also use it to embed images in notes, and (with a helper app) to take screenshots.
Zim isn't installed by default on any of the distros, but is packaged for Ubuntu and Linux Mint.
Spend most of your time in the browser? Why not try out QuickFox notes? The Evernote site is a bit on the sluggish side, which is why I'm not crazy about the Web-based version. QuickFox, however, is a speedy little add-on that lets you take notes directly in Firefox.
What about synchronization, you say? QuickFox saves notes as bookmarks in Firefox, so using a synchronization tool like Xmarks or Weave lets you sync in the background between browsers. Just make sure you've got the QuickFox add-on installed on each computer and you've got a platform-independent note-taking machine at your fingertips.
BasKet is one of the most interesting note-taking apps for Linux. It's full-featured and allows as much (or as little) structure to your note-taking system as you like. Save your notes in "baskets" (hence the name), add files, all types of formatting, lists, create password-protected notes. It's quite a powerful application. It works with the KDE PIM suite, so you can use it standalone or integrated into Kontact.
BasKet does have a couple of downsides. It's not available for Mac OS X or Windows, so it's not a great solution for users who use different OSes at home and work. The development has been a bit erratic as well, and the project has looked like it might die off at times. However, the project seems to be experiencing a bit of revival right now with a 2.0 beta released in March. Overall, well worth a look and a project I'd love to see pick up steam.
For my use, Dropbox and Tomboy in combination are the best tools to replace Evernote. Tomboy lets me keep notes organized and synched between computers, and Dropbox helps sync files between computers. I still rely on email for a lot of info (travel confirmations, for example) because I can get to that from my phone anywhere. The important thing to know is that Linux has the productivity tools that you need. While there's not a direct clone of Evernote on Linux, you can get the job done all the same.