Many of my friends attended Arizona State University, so I've visited Tempe many times. The last time I was in Tempe was August 2009, and I always enjoy visiting the city, even in the Arizona heat. While Tempe often gets dismissed as a "college town", the city itself is much more than that. It is one of the best parts of the Phoenix metropolitan area. The new Valley Metro Light Rail system connects Tempe with downtown Phoenix, so you can get there without a car, and Tempe, due to its large student population, is dense and easily walkable. Tempe doesn't have many major attractions other than the Arizona State campus, unfortunately, but it's a great place for shopping, eating inexpensive food at various restaurants, and relaxing.
The shopping in Tempe is great. There are many unique stores, bookshops and cafes along Mill Avenue near campus, and the outdoor Tempe Marketplace is an ideal place to cool off after a hot Arizona day. Tempe is also home to Arizona's only IKEA, if you want to buy bookshelves and eat Swedish meatballs for lunch.