I recommend the Cryptologic bonuses. Start with William Hill, which pays GBP 5 (about $9) per table hour at 1-2 or NL 100 for the first 5 table hours of each month. TotalBet and UKBetting have similar bonuses, for a total of about $130 for 15 table-hours each month.
Note that most Cryptologic sites (other than William Hill) require you to have a PIN mailed to you before you can cash out, and you may face some currency conversion fees when you deposit to or cash out of UKBetting, TotalBet, and Littlewoods if your Neteller account is not in pounds. So, I'd try putting $100 in UKBetting and TotalBet to play $1-$2. You're still unlikely to bust out before getting the full bonus.
Also on the Cryptologic network is InterPoker, which offers a $90 match each month. It takes a while to clear it at 1-2 or lower (each 5.00 pot clears $0.05), but their 0.50-1 games are quite soft, the bonus doesn't need to be cleared during the month you deposit (find a good signup deal, then put in $90 by Dec. 31st) and if that takes too long, you can clear it in InterCasino by playing games with low house advantages such as
pontoon or
blackjack.
There are also some nice initial bonuses on the Boss network.
I would avoid GamesGrid, Full Tilt, PokerRoom, and UltimateBet. Their bonuses seem large but do not clear quickly, and some of the games are tough.