More tips in case anyone needs to know:
In Firefox 3 (can't remember exactly which version this was included OOTB) there is built-in support for search keywords. In the search bar dropdown box, select Manage Search Engines, select the search engine you want and click Edit Keyword. For older versions of Firefox, search keywords are enabled via
the SearchWords extension.
So for instance, I have 'adb' set as my anidb search keyword. Typing 'adb saint tail' in the address bar automatically searches AniDB for the string 'saint tail'. With this, you can remove the search bar already

If you're comfortable with editing program files, you can easily add other AniDB searches. Go to your Firefox profile folder, look under the folder 'searchplugins', find a file labelled anidb.xml (after you have added AniDB search engine from mycroft.mozdev.org). In that file, look for the following line:
<os:Url type="text/html" method="GET" template="http://anidb.net/perl-bin/animedb.pl?show=animelist&adb.search={searchTerms}&do.search=search&sourceid=Mozilla-search">
</os:Url>
See the part with "show=animelist"? Change 'animelist' to something else to get a different search.
grouplist --> group search
characterlist --> character search
userlist --> user search (stalkerrrrr...)
mylist --> search your own anime list on AniDB (must be logged in)
Just create more copies of anidb.xml, give them unique names (such as 'anidb2.xml', lol). Then in each file, find the section
<os:ShortName>AniDB</os:ShortName>
<os:Description>AniDB Search</os:Description>
Modify it to give each search engine different labels in the search box.