I'd suggest picking up the book The Art of Unit Testing. Chapter 8 covers integrating unit testing into your organization. There's a great table (p. 232) that shows the results of a two-team trial (one using tests, one without); the test team shaved two days off their overall release time (including integration, testing, and bug fixing) and had 1/6 the bugs found in production. Chapter 9 discusses test feasibility analysis for getting the most bang-for-the-buck with legacy code.
