Yes a big question for me too, please someone answer
Hey guys, I'm brand new to this as well and you probably don't need an answer now but I found this anyway:
Flex Builder and Flash Builder both function as Plug-ins to Eclipse, though each also comes in a "stand-alone" flavor - which is still eclipse, but with a lot of the Eclipse functionality torn out for a smaller footprint.
All the best!
StackOverflow always seems to get an answer first (much better forum format I suppose). Good find