We've just switched from CVS to Perforce for source control at work, and the Perforce docs pointed to an amazing paper about branching: Streamed Lines: Branching Patterns for Parallel Software Development.

It is truly a catalog of patterns, but rather than being about architecture or software design, they are about how to branch (work simultaneously on more than one release of software).

It is a stunningly comprehensive paper, laying out 32 patterns (eight each for elements, creation, policy and structuring), then working through variations of a number of them, and ending with traps and pitfalls (13 of them, including merge-a-phobia, branch-a-holic, the never-ending branch, and codeline pudding). I have not read it in depth, but am certain that there is much to learn in it.