Orvieto's beautiful, but it's outside the mainstream of Umbria (sorry, I'm speaking as a perugino). If you aren't driving, I'd use Perugia, Assisi, or Spoleto as a base. Perugia has the most convenient train and bus connections, because it's the regional capital. From there you can take trains or buses almost everywhere. My list of places? It really depends on the season, because as it warms up, there are natural places to experience. But if you're looking at towns, my to-see list would be: Perugia, Assisi, Gubbio, Spello, Trevi, Spoleto. For a more nature-oriented experience, head to Passignano sul Lago, hang out there or take a ferry to Isola Maggiore, where you can hike around the island, enjoying incredible views, and then treat yourself to a decadent lunch at a restaurant near the ferry landing. Spello is just incredibly charming, with polished pink stones, some art, flowers everywhere, and a few really interesting places to eat. Gubbio has an amazing main piazza, an interesting museum, and a hair-raising cable car ride that's more like a ski lift with birdcages. Spoleto is stunning and has great shopping, an archeological museum worth a visit, and incredible views from atop the fort--you take elevators up to the top. And a plug for my hometown, Perugia. It's a college town, vibrant and young, with lots of places to hang out, a few good restaurants, and is perfect for spending lazy days walking around the old town, having a drink, seeing some art, both Renaissance and modern. If you're there mid-July, there's the Umbria Jazz festival, during which the city turns into a giant party. And it's not just jazz--we're seen REM, Brian Wilson, Caetano Veloso, Tony Bennett and Lady Gaga. Bottom line? Umbria's great. And relatively un-touristy.