How hot should my Mac Book Pro Get?

It's normal.

Install iStat Pro to get accurate readings of your temps, among other things

Your temps are most likely perfectly normal, as searching the forum with MRoogle will reveal:

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My Macbook Pro reached 106 degrees !
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Etc., etc., etc.

Install iStat Pro to monitor the internal temperatures. The aluminum bottom acts as a giant heatsink so it's normal that it gets hot.

Depends on what you do on the MBP.

But it always gets hot. The casing is made of Aluminum which absorb heat a lot

Make sure the vent on the back is open and it will be fine.

According to iStat pro, mine gets:

cpu: ~100-110 on avg, 110-120 on web browsing, 160 on skype (hottest app I've run so far - haven't tried iChat yet). Often falls to 97 on idle or somewhere in the 90's.

Bottom case 3 temps: usually in the high 80's or 90's on idle or web browsing, I forget how hot it measures on skype - just checked on skype, bottom is at 99 degrees, not bad considering the cpu is at 160!

gpu: usually about the same as the cpu.

All temps are in Farenheit (sp?).

Watching a movie on iTunes or Front Row on my lap is not a problem, and does not cook my leg. iTunes runs a couple of degrees cooler than front row (Hellboy II). IIRC the temps watching this movie are approx. 117-122 cpu and 97ish bottom case (sounds hot but it's just warm to the touch). Of course, I don't have the MBP buried into the bed comforter, I'm sure that would cause it to heat up a few more degrees. I usually stretch out the comforter around the MBP to allow it some breathing room, especially at the back for the fans

I think this is exactly why they are not called "laptops" anymore but Notebooks