clothes - I didn't bring anything special to wear, although if you want to I would suggest bringing a couple old big tshirts to labor in and for postpartum, ones you don't mind getting icky, because they almost certainly will. Bring a sports bra or bikini top too, they're a good way to be naked but preserve modesty (some mamas don't care, others do). Chances are you'll at some point want to take off whatever gown or shirt you're wearing, laboring mamas tend to get very hot. For the baby, I just picked out an outfit for the hospital picture, the rest of the time he was in the hospital onesies.
other stuff - bring anything you think might help you in labor... find out if the hospital has rice socks and birth balls. If not, consider bringing those. Hospital will likely have juice and popsicles available for you during labor, but if not consider bringing in gatorade. Snacks for DH (mild smelling ones though so he doesn't make you gag with icky breath). Some crackers or something easy to eat and digest for you, just in case you are hungry and need to sneak a bit here and thre. Other tools for labor - massagers, lotions, focal points, CDs/CD player. Chapstick, toothbrushes and toothpaste, mouthwash, hair ties or bands.
In general I (as a labor doula) have found that couples rarely use what they bring for labor. The most important tools that I've seen have been birth ball, rice socks, and the birth partner(s)'s hands and love.
For postpartum, bring whatever you think you might need.. toiletries and clothes to go home in, eg. If you don't plan on spending much time there, you probably won't need much.
I always tell my clients to pack three bags... one for labor, one for postpartum, and a third one with the stuff they look at and think they **might** need but aren't sure. That one can stay in the car the whole time, and if they never use it great, but at least they have it there just in case.