I'd like to stay on Lake Constance for several days to a week and thought it would be fun to rent a condo rather than stay in a hotel. Last time I was in that region I saw what looked like condos. Does anyone have any experience with this. Are there any good websites for finding places like this?
You could google the town you're considering and click under tourism and accommodations (with any luck, there'll be an English version) - perhaps you could find a vacation apartment. I don't know of anything right on the lake (except I did see one in Konstanz last year) but there are accommodations to be found under "Urlaub auf dem Bauernhof" in that general area of Germany, sort of like "agriturismo" in Italy.
Try www.homeaway.com
I use vrbo.com for vacation rentals.