The X-Base is a collaboration of work made by xOR and Der_Herr. The X has become kind of a corporate identity for these projects (usually programming related stuff) as for the names and logos of these products. It either precedes the project name or is contained in it.
Being a base the X-Base is the starting point to get some information about each project or to find links to related resources. It is not intended to give in-depth information about each project but a first overview and the right links to find detailed information.
All projects more or less share the same resources. Their respective pages here will directly link to their area within these resources, this page will only give an overview.
The subversion repositories for each project are at svn.x-base.info. Usually they don't allow anonymous access, you need to get an account from xOR to access them.
The forums can be found at http://forums.x-base.info, each project has its own sub forum there.
The X-Base Wiki can be found at https://wiki.x-base.info. Each project has its own area there.
X-Base projects are using Mantis as bug tracker. It can be found at http://bugs.x-base.info.