Mclaren/Ferrari
Red Bull/BMW
Williams
Renault/STR/FIF1
Toyota
Name TBC by Ross Brawn
The reasons for the and/or's is because I feel the drivers will play a part. For example I think Lewis might be quicker than both Ferrari's but both Ferrari's to be quicker than Kovy.
I think RBR will be fast, and BMW will also be quick (they've quietly been getting on and I feel they'll be strong) STR will be quick (same basic car as RBR) but I feel their driver line up won't be sufficient to keep them up with their sister team, I reckon the FIF1 car will be fast enough to give them a run for their money and I've ranked the Renault up highly because I feel in the hands of Fernando it'll be quick-ish (well quicker than the Williams which I've ranked above them because I feel the TEAm will perform better than the aggregate performance of Alonso & Piquet...I think Piquet is really struggling atm - hope for his sake I'm wrong)
I've got Toyota low down for no good reason, just process of elimination, sorry. I have nothing to base that on, just a hunch. And The Ross Brawn team will be slow purely because the poor sods have had such little time with which to get prepared.
I DO think however that there will be some changes mid season.
Final disclaimer....I have NO FACTS or anything on which to base my assumptions, please don't flame me because you might disagree, its just a hunch and a bit of fun to try and predict it.

Silence is golden when you don't know a good answer.