It's sort of a tradition for us to attend the Tempe Arts Festival. There's lots of stuff to look at and buy. You can find everything from art pieces costing tens of thousands of dollars to small craft presents costing just a few dollars. And being that the Fall Festival always takes place just before Christmas its a great place to find unique gifts for friends and family. There's even an entire section devoted to food items that you can't find elsewhere and a kids section with crafts and games. Plus, there's tons of entertainment for all ages including jugglers, bands, dancers, musicians, and other things.
If you want to avoid the hassle of parking, just take the light rail to Mill Avenue, but even if you drive, there are plenty of garages and surface lots available for a small fee.
Enjoy!