Right now there are a few main categories of Fat Burners that are all stackable and don't really overlap with eachother.
Stim Loaded:
OxyElite Pro
Adrenalean
Forged
Medium to Low Stim:
Alpha-T2
Eviscerate
Stim Free:
Lean Xtreme
DCP
Lean FX
Thyroid Booster:
Alpha-T2
Targeted/Spot Fat Burner:
Alpha-T2
Eviscerate
You can essentially stack any product from one category with another from any other category. Hence all the stacks Orbit has!
Obviously i didnt list every supplement out there, that would take forever