Yes, you can have 7 adsense ads on a page (the official Google blog from their AdSense team.)
3 ad units
2 AdSense for Search boxes
1 Link unit
1 Referral button per product (i.e., 1 AdSense referral button and 1 Firefox plus Google Toolbar referral button).
So if you are building a site monetized by AdSense you might be able to make a little extra money by putting in a couple of the new formats of AdSense ads. I have been playing around with them and have found some (like the linkbar) to be pretty darn useful!