and I'd like to spend somewhere between 2-6 days at each place.
Ben Franklin famously said "Fish and visitors stink after three days." Just something to keep in mind. :)

Seriously, don't consider these places freebies. Even someone happy to see you and have you stay with them would appreciate you pitching in to buy groceries and/or taking them out to a nice dinner or something else fun as a way of thanking them. So make sure you budget for this.

Buck's suggestion of $100/day is a good general guidelines. If you want to work out a more individualized budget, check out these tips.