Phil and Teds are awesome and lightweight go-anywhere strollers. Wish we had bought one originally instead of the multiple jogger/umbrella/graco ones we had with our 1st child. When our 2nd was coming we needed a stroller that could do 2 kids when needed, and we ended up getting the Sport which allows for a 2nd seat that can mount to the frame inline and behind the 1st main seat (plus the main seat can lay completely flat and accepts most infant seats). It's very mobile, easy to use, and lightweight. They have even better versions now but I highly recommend checking them out. They're not cheap, but worth every penny.
http://philandteds.com/index_home_freaked.htm