There're a lot of embedded options around... cheap devices and good processing power as well.
As Fran already sad it's nice to understand your minimal requirements and what kind of tasks you want to achieve. Are you planning to have another Access Point for some cross compiling stuff and wireless jobs ? Take a look at ASUS (WL500/700/...) or DLink devices. Are you planning to use a real embedded system ? Soekris Engineering cards are fine as well as AXIS or AMD Geode cards. Do you need a quite decent CPU processing power, a small ATX form and a cheap price ? Intel Atom for example.
What about :
- Your budget
- power consumption
- features needed (I/O, serial/usb ports, disk controllers, audio, ...)
- preferred CPU (MIPS, ARM, x86, ...) if any
- preferred cross compiling toolchain or Linux environment (OpenWRT, custom, ...)

I found Mr. Gatliff several years ago. He may be able to help.
He does training seminars for embeded linux systems.
Hardware is a part of his seminars. I have found his information informative.
Sincerely, jas011

Mr. Gatliff may be reached through his web site at:
http://billgatliff.com/

Hello Olaide,

The wrt54gl was a beautiful piece of hardware, I have one here as back-up. When I bought my next router, I wanted it cheap, with Gbit nics, wireless-n, usb-port, and most importantly solid support from OpenWrt. I ended up with TP-Link TL-WR1043ND providing all of that. You can install OpenWrt (or alternative third party firmware) user-friendly through the web-interface. It has a Atheros based wireless with excellent linux support. Compared to wrt54gl it has twice the cpu clock, twice the amount of flash storage and twice the amount of ram, and it costs about the same as a wrt54gl. That's a bargain I am sure Soekris is nice, but it is a different price range.

Good luck!

Hi...just take a look of supported devices by dd-wrt, a custom firmware that is a lot more powerful than any stock firmware. If the device can run it, then is a good device! http://www.dd-wrt.com/wiki/index.php/Supported_Devices.

Personally I would use TP-Link TL-WR1043ND for SOHO.

I use all range of PCEngines ALIX:
http://pcengines.ch/alix.htm
Prices are usually below 150 USD for board
and below 200 USD for board+case+flash+power supply bundle.

Personally advise you to use ALIX2D13 board.
US: http://www.mini-box.com/Alix-2D-Board-3-LAN-1-MINI-PCI-RTC-battery?sc=8&category=1361
EU: http://shop.varia-store.com/product_info.php?info=p724_ALIX-2D13-Mainboard--500MHz-3xLAN-1xMini-PCI-IDE-USB-RTC.html

You are free to use DD-WRT or even bigger player - Vyatta on it.
BTW there is a comprehensive HOWTO about using ALIX and Vyatta together:
http://www.vyatta.org/forum/viewtopic.php?p=38450

Good luck!