I search lots of different sites regularly, and I knew there had to be a way to customize the search field of Camino so that it would do more that just Google and Google Images. If you look in ~/Library » Application Support » Camino, there is a file called SearchURLList.plist. You can edit this file in a text editor and add your own search engines. Always save a backup of this file first, of course.
For example, I added the following two lines to search the PHP Function Reference on php.net:
<key>PHP Function Reference</key>
<string>http://us2.php.net/manual-lookup.php?pattern=%s</string>
I have also set it up to use an online spanish dictionary (Tomisimo) and Wikipedia, amongst others. I am using Camino 1.5 and OS X 10.4.10.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20070724065211856