In addition to the DVD NFL flims puts out every year for the SB chamion the Pats have produced their own DVD's called Three Games to Glory I, II, and III which focus just on the post season wins in their Super Bowl runs. It wouldn't surprise me if the Steelers do the same thing.
That would be cool. I definitely want something to commemorate but I've never really dug the t-shirts the NFL sells, not enough team colors. Anyway hanging out in the geek world I'm on the mainline for free t-shirts and now have a hard time justifying paying for t-shirts, especially at NFL official merchandise prices.