I just started using Sitter City two months ago. Have you tried it? I was looking for a sitter for particular hours (really, the first sitter I will have ever had other than my parents and in-laws) and was having trouble. So we joined Sitter City and found a few!
Once you join, you can submit a profile (almost like a personal ad) and sitters can respond to your inquiry. You can approach them and set an interview from there. Sitter City offers a background check (I believe it costs extra for the sitters, so not everyone does it), references, personal statements, pictures and more. I found it really helpful and will definitely use it again the next time I am looking.
If you are interested in trying it out, Family Finds is offering a one month subscription to Sitter City for only $17 right now. That’s 51% off the normal price! If you are looking for a sitter, do yourself a favor and check this site out.