It might be a while before i can put together another combo challenge, but luckily quite a few people have taken the initiative to issue original challenges of their own. Look these over and give them a quick try if they strike you as interesting.
SF4 Ryu Hard Trial Combo Level 8 by AZ
This is a suggestion for a hard trial combo.
Ryu : FA lvl3, dash, 6HP, 2MP, 2HP, 236P, FADC, 2MK, 236P, FADC, 2MP, 2HP, 623LP, 236236PPP. (I believe it works on Sagat only …)
SF4 C.Viper Seismo Challenge by Shaunt29
Pick an opponent that can be touched by a Seismo Punch in the far corner while crouching. Set the dummy character to Crouch and All Block. String together as many superjump-canceled Seismo Punches as you can.
T6BR Combo Challenge: Rage Death by shizo666
Challenge: Execute an Unescapeable Rage Death Combo without Breaking the Wall or the Floor.
Conditions: No Big Characters as Opponent, No Unblockable Moves, No Power Charge, No Counter Hit, 100% Unescapeable
Good luck! Feel free to discuss potential solutions here if you like.