I think it depends on where you live! I'm in NYC so going outside means going to playgrounds that, while an awful lot of fun and LOOK clean, are probably pretty damn nasty. Also the black rubber stuff that you walk on can get hot (in which case my baby wants to hold my hands to help him walk). So we use these outside:
http://www.target.com/s/177-7955658-...1&searchPage=1
basically cheaper robeez!
Now that he's about to walk I like Stride Rite and Umi and Simple shoes. Still very flexible but won't be penetrated by stray glass or something else sharp.