You're probably going to get alot of responses recommending 3M Ultrafina, so here's the first one.

UF works *alot* faster than 106 does. Pretty much four passes and you're done. Only complaint is that it's a slinger, especially if you're used to using 106. 1Z High Gloss is really good, too. Very easy to use and it doesn't take as long as 106, either.
Menzerna Intensive Polish is a good substitute for SIP if you're not working on hard clear. It's easier to use than SIP, but not nearly as powerful. HighTemp .357 Magnum is pretty good, too. Presta UCCL and UCC are pretty big guns. Quite a bit bigger than SIP.