Not much since the ephedra ban, and I've tried MANY. Trimspa, zantrex, relacore, nv, stacker, etc etc. None of it worked for me.
I also took a prescription before though-phentermine-and it worked really well. I didn't gain the weight back when I quit taking it...atleast not until I got pregnant AGAIN.
If you really want to take a pill, your best bet is asking your doctor first. Prescriptions are monitored by the fda, and even if it costs more than picking up a bottle of the latest trend, you will still save all the money I've wasted on trial and error. Mostly error.