Am I forgetting anything for my race tomorrow?

I guess you're not wearing a wetsuit otherwise that needs to be added to the swim list.

Number belt, or are you pinning number on your T shirt?

If it's USAT sanctioned, membership card, and photo ID.

Some races don't use frame numbers.  So you may or may not have to deal with that.

Sometimes the frame numbers have adhesive backing that you peel off and stick the number around your top tube or seat post.  It's kind of a pain to get off afterwards, and can stick on your pretty paint job.  So what I do is bring a piece of plastic wrap.  The clingier the better.  Wrap that tightly around the top tube or seat post, then peel off the backing, and apply the number.

If it's one of the numbers that uses ties to secure it, it's not a bad idea to have a few extras with you.  Sometimes I find the one supplied aren't long enough.

If you have a watch that does laps - that's nice too, to track your time in the different events.  Don't worry about it if you don't have a basic waterproof watch though.

For after the race, put a couple of extra water bottles in there with a washcloth.  If they have a shower, great, otherwise it feels REALLY good afterwards to get your washcloth wet and run it over your hot and sticky self.  Especially the face.  Maybe even dumping a water bottle on your head afterwards. Oh, lotion is good as well to get the race numbers off.

If it's going to be hot, I'd suggest filling your water bottles 1/2 way tonite and then filling them the rest of the way with water before you leave tomorrow.  Also, bring one unfrozen bottle, in case your others aren't thawed out when you need them.  Nothing better than having a nice COLD drink on the bike when it's hot outside.

Bring a comfy pair of sandals for after as well.  Your feet will be real happy.

Good luck!!!