Spam Pal
http://www.spampal.org/
Both are 'anti' spam programs that utilize various features to help
stop/filter/combat spam.
There are advocates of both, and many times it comes down to personal
preference as to which is 'better'
spam assassin is a server side filter.
spam pal is a client side filter.
Both are free and easily configurable if you can count past 50.
Both use dnsbls /you/ select plus some other stuff.
I think you have the links from Dan.
I find Tbird + spampal doe a good job of catching most spam - but then,
I use the spews bl and block all of Asia save AU and the Kiwis, all S.
America, and most of Europe, all RU, and Lake Louise.