Can anyone recommend a source for info on renting a furnished studio or apartment for a longer stay in Lisbon (a couple of weeks or a couple of months)?
Rick's Portugal book (p. 114) recommends www.cross-pollinate.com for Lisbon apartments. Happy planning!
VRBO is my trusted site for renting apartments anywhere. When we stayed in a fabulous duplex in Lisbon, we stayed in the Alfama, which was great fun. A gorgeous view of the Tagus, a continual cool breeze, plenty of room, and a marvelous neighborhood. Good luck!