Just found this, had heard of Rollyo before, but didn't know you can make custom Firefox search engines with it http://www.rollyo.com/firefox_search.html
Go to that page and type a name, and then in the second box put:http://www.donationcoder.com/
And voila, it prompts to install the new search engine, and now you can search DC from firefox
I think Find + Run Robot also has a DC Forum search function, but this can search the main site too
Also, you can add multiple websites, or have as many custom engines as you want!