I've narrowed it down to three cameras?

Canon XSI 15 mp
Nikon D3100 12.1 mp
Olympus Pen EP-1

I'm a beginner with an SLR… I mean I've done alot with my minnolta 35 mm film camera but i'm stepping into the big leagues… Suggestions?

The pen is not a DSLR, it's a compact with a big sensor and interchangeable lenses. The canon was Canon's entrly level camera announced in 2008. The d3100 is nikon's 2010 entry level model, better sensor, video to name just a few differences.

Anything you've learned about iso, aperture and shutter speed with that minolta is still valid.

I would go with the latest model being the 14.2 Mp D3100.It was designed to make it easier to transition into digital SLRs and has the title of best selling entry level dSLR. The pen is just a point and shoot with interchangeable lenses. I can't say anything about the XSi because I have never used one. Don't go by megapixel ratings they are just a wow factor with no real purpose but to claim to have more than the competition.