What are you looking to back up?
The majority of stuff, (contacts etc) are backed up to the google account you used to setup your handset. You can check this by accessing the contacts section of your gmail account via a PC, if the numbers there correspond to your phone book, you're sorted. Likewise, apps you have installed via the market should automatically come with you as the'yre tied to your google account. Again, you can check online
here. All pics, vids etc. are on the SD Card so you wouldn't need to worry about them, but if you want to be sure, you'd take the SD Card out when resetting.
If you can't see the contacts via your gmail account, follow
these instructions and that should ensure contacts are backed up.
If you want to back up SMS etc, they can be done with
this, but there are plenty of alternatives on the market.
You won't be able to save app data unfortunately unless you're rooted.
Let me know if there's anything else you want/need backed up and I'll have a dig about to see if there is any way of doing so.
