If no one has offered you a lot of money in the last 10 years, it's likely worthless IMHO
You might get really lucky and be able to sell it to another domain speculator, or someone that really really needs it.
What's the last big website to use a 4 letter .com name?
There's digg and hulu at least. I can't think of anything more recent. (there's also xkcd.com but it's not exactly big)
Short URLs are great, but given the 4 char domains left you're probably better off with a longer and more memorable one.
Hey, I take offense to being lumped in with domain squatters, because I have the domain name for purely personal reasons and I would never sell it. I was just curious about how much they go for, that's all.
(My first name is Idoh and I own idoh.com)
Even if it ended up being worth a fortune? I guess I would be hard pressed to sell my name domains too. But for enough money maybe.