I LOVE Dim Sum and wish I could do it more often. We've done it in Boston a few times and many many times when I was a little girl in China.
I wish I could remember the names of the yummy stuff for you. My nieces would know (they are half Chinese and still speak it).
There is this one white (rice) noodle that you can get and they pour some yummy brown sauce on it, boy is it delicious. Here's a picture though. YUM!
You can't go wrong with the items that look like meatballs (Shui Mai).
Also, you should try 'sticky' rice. It comes served in lotus leaves. Its very delicious. It comes with a variety of ingredients like pork, beef etc...
Also, another yummy item is a Cha Sue Bun (Char Siu Bao). It is a white bun with Roasted pork in it. YUM!
Here's a link to a picture with typical Dim Sum dishes; the bun on the lower right is the Roast pork bun:
http://commons.wikimedia.org/wiki/Image
imsum_breakfast_in_Hong_Kong.jpg
Those are some of my favorites!