Just in case you're looking for more after beating the game, the dev himself featured some user-created levels he liked on his website. I know I'll be checking them out.

If you know of any other good depositories of such please feel free to add them here. The more the merrier. ;)

I think most of the time, user created levels of VVVVVV are much too hard. Some are really good and balanced and creative, but many fall to the misconception that harder is better. After having played some, I realize that the base game is really well balanced and not too difficult.

Well, users.... The problem with user-created content for any game is curation. Getting to the good stuff is damned near impossible in an environment where garbage overflows. Word of mouth can carry a few awesome levels, but usually people who are interested in what others make end up trudging through oceans worth of detritus to get to the few good levels.