Hmmm . . . good question. Well, I'm sure they were painful at the time (I did take some pain medication because things were getting really intense), but I don't really remember that anymore. My contractions were pretty regular all day long (like, from 7 in the morning until I went to the hospital for the second time at 4ish pm) and just got more intense and longer. But we went to the mall (we even tried to buy some sheets, but I finally told dh "you know, this is just not the time. I can not concentrate on what colour and fabric I want my sheets to be right now."
), and I went for walks and had a nap while I was having contractions (well, you sort of doze, then you're woken up, then you doze off again. It wasn't until my water broke and I was about 6 or 7 cm dialated that things got really intense (around 4 pm).
But as for what they feel like . . . for me it was just like my whole lower abdomen and back were being clenched really tight and then relaxing again. It was different than the pain of, say, breaking your arm, which is kind of constant. I don't really know how else to describe them.
I found, the same as pp, that the best thing to do is just get "in the zone" and sort of ride them out -- they do sort of ebb and flow, and you just sort of find that place inside yourself where you can let your body take over. Just relax and don't try to fight them or hold them back. Its easy for me to say because I was only in hard labour for 5 hours or so and I did take drugs.
I was totally alert for pushing, however, and that was awesome (again, it was an hour and very productive, so I can't speak for what it would be like otherwise). But again, there are breaks -- you push, then stop, then push, then stop. There's a natural rhythm and rest time built into it.