Neteller
Firepay
Most credit cards do not allow you to deposit to poker (or any gambling) sites. Debit cards are not much better (although some are supposed to work, most don't).
If you have a bank account and are not in Maryland (I think it is Maryland
) then Neteller is the way to go. You can get free transfers to/from your bank account (if you are willing to wait 3-4 days-If you want it instantaneously there is an 8% fee for the transfer).
If you are in Maryland, Firepay is pretty similar (I hear at least, I use Neteller).
There are other ways (look at PartyPokers list of deposit methods that can get money directly from your bank account/debit card and put it in your poker account. Even if it is just an imagined comfort, I personally like the buffer that Neteller provides between my bank info and the poker site.