Most bigger grocery stores carry them in the health foods section plus you can order them on line from Amazon and netrition -- and I'm sure there are a lot of other sources.
I've used them, and one thing I've noticed is that if you use more than the suggested serving size, it definitely impacts the taste. By that I mean deciding that since they have no calories you can use the entire bag for a plate of spaghetti......well, it didn't work out too well for me. When I used the recommended serving size, it was just fine.
Mini Goals: Move Here Weight (2005): 344 (Done), Stop Smoking Weight (1997): 333, Mom Remarried (1990) 313, Twoderville: 299, Move to NC (1989): 280, Closer to 200 than 300: 249, More to Come....