FT's public tourneys are so freakin' hard to place in, but I do enjoy the Rush NLHE and Rush PLO freerolls.
I used to be a big advocate of merge network freerolls, but ever since the payout structure changed, it's just not really all that worth it. They're easy enough to place in (merge competition is just really, really soft in my experience), but to play for 3 hours just to get a $2 or $11 satellite ticket really bugs me.
I usually try to play in the satellite freerolls that FT offers for the Daily Dollar and Ferguson tournaments -- The Ferguson satellite is nice. Turbo, 2700 limit, and top 100 spots pay $1 tourney ticket. Not a huge payday, but it'll get you into something that could build your bankroll a little further, and it's not a huge time sink.
Daily Dollar satellite is a super turbo (300 chip starting), so it's a little more of a crapshoot, but it's not impossible to cash in it, though it is still a large field (7500), but top 200 get entry in that one.
If you're into PokerStars, though, the PokerSchoolOnline (PSO) skill league tourneys are the way to go -- if you work your way up through the leaderboard, the payout is well worth it, especially if you're an 'active' player by their standards (I think 20 fpps are required in the last month). The individual freerolls don't pay more than a couple of bucks each, though, so if you're not grinding for leaderboard position, it may not be for you...just my thoughts, though.