Well, the only trick i know would be on the Samsung Moment. you really didn't specify =(
You call your cell phone.
while your cell phone is ringing, repeatidly press your home key, but do not answer
hang up on other phone.
Should bring you into your home screen but be aware, it will lock agen!
also, if you remember your gmail account but not your password, you can try "null" for the password, works on all andriod phones.
I think it MIGHT depend on the make and model of your phone, but generally speaking, to unlock your phone (once you've locked it), you either type the last 4 digits of your phone number OR you type 0000 (i.e., four zeroes in a row). If that doesn't work, I would suggest calling in to customer service and seeing if they can help. Otherwise, you may be stuck doing a hard reset where you will most likely lose all of your saved data if it's not saved on a SIM card.
There are only a few phones that have a sim card, a select few blackberrys and the HTC Touch Pro 2. However, most of the smart phones have there on way of backing up contacts automatically.
Andriod: Gmail account that is on the phone. if you forget the information you can only go to palm, sprint doesn't have it
Instincts (all models): Sprint Mobile Sync, make sure you get a copy BEFORE putting another phone on that line, they WILL BE DELETED
Palm (Most Models): The palm profile that was setup during activation. if you forget the information you can only go to palm, sprint doesn't have it
Most lower grade phones have the option for Wireless Backup, charges $2/mo for it, but its worth it if you have alot of contacts, no one expects there phone to break!