With her two kids, Grace Welch found out what we've been finding out lately: it's damn hard to keep a wiggly kid on a rectangular changing pad.
Unlike me, though, Grace did something about it. She designed a circular changing pad, added some pockets to tuck a diaper and wipes, and started making them, in six different patterns named after her kids, her husband, the grandparents...and Brown University [in case the kids don't get into Harvard].
They look kinda purse-y when they're folded up. So throw it in your bag, or make sure you wear matching shoes.
Check out Patemm Pads at Patemm.com. [Thanks, Jonathan]
You'll discover after a couple of years (and a couple of kids), that it doesn't matter if the baby is on the mat, as long as his butt is. (I have boys) For this any shape will do as long as its larger than a square foot.
If you are at home or in a clean environment it only matters if the butt is on the pad, but if you are out and about, it is nice to know the hands and head aren't touching anything gross.
This really is the best product ever.