These are all free to some degree. Pretty much the best I've found. Check them out.

Friend Finder
A sugary-sweet personals, wholesome as apple pie!

Adult Friend Finder
The 9 1/2 weeks version of Friend Finder!

Sexy Ads
Lots of alternative ads here.

Matchmaker
Tons of sites, regional, alt, lesbian, you name it!

Singles Heaven
A free singles site. Not bad.

Alt.com
You name it, they have a category for it! Extreme personals!

IWantU
A must for personals. Free ads and email notification of mail in your box!

American Singles
A little difficult to navigate, but, hey, it's free!

Dating 2020
Excellent, very comprehensive matchmaking service.