Since Umbagog Lake is in the less-traveled region of NH, I figured it might be helpful to post a report for future travelers.
We camped at Umbagog Lake State campground for 2 nights over Labor Day weekend. It's a beautiful campground in a remote area. They have remote sites all around the lake that you can camp at, but we chose to stay at the main campground (too expensive for the boat to and from the remote sites!).
On our drive up on Saturday, we stopped off in Franconia Notch and walked to the basin and along the cascades trail for a while - beautiful trail. Then we drove to Umbagog.
The next day it was quite cool and windy, so in the morning we drove to Dixville Notch and checked out the quick trails to the waterfalls and baby flume on the side of the road. Then we hiked up to Table Rock on the short steep trail. Amazing views at the top, although I was a little scared to go right to the end of the rock because it was really really windy. The hike up is very steep - hands and knees required sometimes, but it's not very long and the view is totally worth it. I might not want to do it if it was wet and slippy though.
Afterwards, we had lunch at the Panorama golf course at the Balsams hotel. The view was great, the food was fine but nothing special, and we (mid-20s) were definitely the youngest there.
After lunch we weren't sure what to do. We wanted to go caneoing on Lake Umbagog but it was still cool and windy with occasional showers and we weren't sure how much fun it would be, so we ended up driving to Rangely in Maine. On our way we stopped off at the Umbagog Wildlife Refuge. I didn't realize this was a separate area from where our campground was. It's beautiful, but unfortunately we weren't able to appreciate it fully as we weren't canoeing. Note that they don't rent canoes at the refuge - rent them in Errol.
Rangely was a longer drive than we had anticipated but it was a nice drive, and again the lake is beautiful. Much more developed than Umbagog which really only has the campground.
This was a very last minute trip (as we had canceled our trip to Maine because of Hurricane Earl), so I had no time to plan,( and I''m usually a big planner). I really wish I had looked more things up - if I had known more about the wildlife refuge I would have probably gone canoeing regardless of the weather. There is also good information about specifically where to spot moose on the refuge website that I wish I had seen before we went. http://www.fws.gov/northeast/lakeumbagog/ On the other hand, Franconia and Dixville were great, and the scenic drives were beautiful. I just wish we had spent a little more time out of the car.
I would definitely go back to this region, and highly recommend it if you want to camp in a beautiful and peaceful location with a good chance of seeing wildlife. Note that there aren't lots of tourist services here - Errol is the nearest town and is small, with only a couple of restaurants, a grocery store and gas station. But if I go again, I'll be better informed next time. I'll kayak around the wildlife refuge, look for moose and visit Dixville Notch again.