After doing a bunch of searching on CodeProject, I decided to see if there was a search plugin for Firefox that worked on that site. I couldn't find it, so I figured "how hard can it be?" and created my own. I'm not completely certain that it's as great as it could be, but for a first effort it seems to be working just fine.
To use it, download this file and then place the codeproject.* files into your "searchplugins" directory (under the Firefox program directory). Once you do, you should have "CodeProject" listed in your search engines, along with the little CodeProject mascot.
I'll submit it to the Mozilla project before long, but figured it can't hurt to get it out there and get some feedback. On this page, they mention that their turnaround time for making these available is sometimes a few weeks.
You can edit the .src file in a text editor to change the options used by CodeProject when you search. Let me know if you find any improvements or problems... enjoy!
Disclaimer The opinions expressed herein are my own personal opinions and do not represent my employer's view in any way, shape, or form. Seriously.