Websites with personal ads and chat rooms for HIVers range from those for people who just want to talk dirty to ones for hopeless romantics:

Living Positive
Easy-to-understand listings of personal ads, classified by gender and sexual orientation and searchable by state. You can also look for roommates, jobs and other classified services.

Positive Personals
Straight and gay HIVers can search for personal ads according to where you live.

Chat rooms and a great personal-ads section (with photos that often even match the descriptions).

Positive Connections
For straight HIVers. One snag: In order to respond, you have to send a snail-mail letter and pay a small fee.
Chat rooms for gay HIVers with conversations in real time. Not necessarily the place for those seeking marriage proposals, and queer gals won't find many others here.