LetsDateFree.com (if i do say so myself)......... At least it genuniely is free to use - alot of dating sites that claim to be free forget to mention they're free until someone sends you a message and you want to read it.
HOTorNOT is pretty good - a very addictive photo rating site with a "meet me" segment if you want to try take things further.
Interpals is good if you want to start out as penpals first, then take it further if / when the time is right.
PlentyofFish claims to be the best and most popular (certainly the most heavily advertised).
There's various other "Facebook apps" that allow you to date on facebook through them.... though most of them these days they've been taking over by fake profiles that turn out to be some sort of spambot / instant messenger spambot that's trying to promote some mucky webcam site.
For more dating site options........