I agree with what I've read in the past few days about places to go in Umbria. We spent two weeks outside of Assisi last year, and had a great time exploring the hill towns. We rented an apartment at a farm, a REAL farm, and had a lovely time http://www.brigolante.com
Assisi itself is wonderful. Definately go to the Rocca and the Hermitage of St. Francis. Also, toursity as it is, the church in Santa Maria degli Angeli is where St. Francis's litte church is located (inside the big church). Also, to stay connected, there are a few internet points in Assisi.
We enjoyed many small towns: Spello, Bevagna, Montefalco, the wine history museum in Torgiano. Perugia is always nice, and the art museum mentioned before is very nice. We didn't get to Todi, so we'll visit that town this summer. We visited Orvieto several years ago, and the duomo is truly a work of art!
We love Umbria - plenty of beautiful spots and not at crowded as Tuscany.