Bonuswhores.com has a pretty good list of sign up bonuses. I would suggest you stay away from the larger bonuses such as Full Tilt's $600 until you have enough money to take full advantage of them. It is worth paying attention to the terms of the bonuses, some of them are a lot easier to clear than others. Also, some of them will only be paid once you have cleared the entire bonus. Avoid these ones if you aren't sure if you will play enough to complete the whole bonus before it expires. I would advise sticking to the larger sites that you have probably heard of for security.
I think Titan Poker's sign up bonus is relatively easy to clear at low stakes.
As mentioned above, investigate if it possible to get rakeback before you join a site, it is often not possible to get it once you have signed up.
I have never used Neteller or Moneybbokers so I can't help there, sorry.