I met my wife on eHarmony and had several good matches thorugh the process, but didn't take them too far. I was on match for a while and I found it to be like MySpace. A bunch of people making free profiles and staring at each other. I talked to a few, but only met one girl from match, and she was shady as hell. Supposedly a really nice girl, but the situation was very strange. My old boss met his wife on Match though, so it could have had something to do with my age at the time.
I did it because the girls I was meeting when going out were absolute trash. I got tired of meeting skanks that had no ambition in life. It sounds like you're just not comfortible in the bar scene right now, and you're not ready to date either. If you're just looking for friends, people to hang out with, or things to do, I would follow the advice given earlier and join a group/club of an activity you like to do. You'll meet people in a relaxed setting, possibly build friendships, and start to feel more comfortible in your own shoes. I think the worst thing you could do right now is get into a serious relationship, if you're still grieving over the loss of your husband, which is potentially what would happen if you are on a dating site. Take this time for yourself.