The number of packages written in Julia continues to grow at a superlinear rate. At the time of writing, there are more than 600 registered packages and many more available from programmers on GitHub but as yet unregistered with the Julialang group.
As usual, developers tended to make use of their own packages when writing new ones than those of colleagues and eventually those from the community at large.
This has led to the formation of groups of developers with shared interests, these are termed community groups and are referenced on the Julia website as part of the community section (http://julialang.org/community/).
Some of the larger groups such as JuliaStats and JuliaOpt maintain their own websites separate from GitHub and ...