OK, will probably get flamed on here by the moral guardians but here is my $0.02
Many moons ago I was several months out of a particularly unpleasant break up and although I was on the mend and largely back to my old self I was still not in the mood or indeed ready to get involved emotionally in a relationship, but I was horny as hell. Having had a fairly lively sex life before I was climbing the walls having not had any 'action' in over half a year. I did not want to join a dating site as to me that meant the possibllity of leading women astray and people getting hurt when they find out you want a slightly more casual encounter. Most of the mainstream sites have a 'just friends/companionship' options for your profile but that still seemed a bit opaque and vague for my liking. So I took the plunge and joined a sex contacts site
I was not really expecting much luck as it seemed to be about 90% men so the odds were not in my favour! But I pressed on and started to email some interesting local women and to my pleasent surprise got some replies. After exchanging several emails with one women and chatting on msn we got to know each other a little and indeed generate a bit of trust. Yes, the profiles can be quite explicit in terms of the more 'niche' activities as you have the option to list your 'interests' (anal, dressing up, dogging, oral, S&M etc etc) but at least you are being honest with each other. We agreed to meet and it was just like a normal date, we met at a wine bar, she was a professional, smart, very funny and sexy women who was in a similar situation to me. We ended up becoming 'friends with benefits' for the next 18 months. We only saw each other maybe once or twice a month, and it was not just clinical sex, we would go out for dinner, watch a film, go to the theatre, generally have a laugh and before having mind blowing sex later that night. Its not for everyone, but for the pair of us, right there and right then it was just what we needed. We were very honest with each other with regards to our feelings and nobody got hurt as we both knew that although we got on very well there was not quite the 'romantic' chemistry that would have made a long term relationship unlikely. We knew it would not be for ever and sure enough she ended up meeting a guy who she really did want to get romantically involved with so we parted company. By that time I was actually ready to get back on the wagon and ended up joining match.com. It is possible.
There are lots of timewasters on these sites and lots of married/attached people although they are easy to spot after a while. If you have the patience there are some normal fun people to meet and have fun with and you get to 'scratch that itch' without anyone getting hurt