Do you want access to the source code? Our public git repository is documented here.
An overview of the releases since Varnish 2.0 can be found here.
Trac is an integrated wiki and issue tracker. The Wiki is mostly for development resources but there is also a lot of interesting VCL there. You can find our trac here.
An overview of all available extensions written for Varnish Cache as Varnish Modules (VMODs in short) can be found here.
Several useful utilities exist that will make operating a Varnish server esier. Take a look at the utilities page.
If you're stuck you can see what support options you have.
Thanks for #VUG8 in Berlin!
Commercial support from Varnish developers is available.