http://boards.immigration.com/forumdisplay.php?f=31
The sticky thread at the top has all the FAQ's you will need.
I applied for my EAD2 and AP2 3 days ago. Here is what i sent them
1. Cover Letter
2. Copy of confirmation receipt notice (I-765).
3. Copy of confirmation receipt notice (I-131).
4. Copy of pending I-485 receipt.
5. Copy of pending underlying I-140 receipt.
6. Cut-out mailer of current EAD card.
7. Copy of Current EAD card (Front and Back)
8. Copy of Old EAD card (Front and Back)
9. Copy of I-94 and H1-B Visa Stamp in passport
I think the online application process is not very smooth. There are a lot of confusions which have been discussed in the thread above. Also, If I were not to read these forums, I probably would not have sent any supporting documents. They dont ask you to do that anywhere in the process!
You will notice that the link above asks you to send several more things like biographical page of passport, copy of DL etc. etc. I did not send these as the confirmation receipt specifically said that "do not send any identification documents unless asked for" or something like that.