Strangely enough before seeing this post I got out my 45s earlier today to take a look at them. I have about 20 and most of mine are from the 70's. I think the most valuable will be the Devo Mongoloid/Jocko Homo single. I'm not sure if it's a first or second pressing but it appears it might be worth anywhere between $10 and $35. I'll probably take it to the used record store to see how much they'll give me for it and some of my other ones.
I don't ever play them anymore, so I might as well sell them to get some money to buy more CDs or digital music that I want.