I'd suggest either PokerStars or Full Tilt Poker as they seem to be the best two outposts remaining.

However, if your country doesn't have the restrictions we do, I might suggest either Party Poker, Sun Poker or Mansion Poker. I enjoyed those sites back when I could play there.

Look for a site that offers rakeback as that is a bonus for your bankroll.

If you have only $100, I'd be a bit leary of the NL tables. Typically you want to play at a level that you have at least 15-30 buy-ins to avoid the variance and busts that happen with NL.