Which "must have" ERISA/EB books/outlines do people recommend for someone in this field?

I have several recommendations:
1. This website is terrific. I use it everyday.
2. The "Panel" series of textbooks is pretty good, and is generally user-friendly.
3. Other texts of long-standing, such as "Pension Planning" (publisher is Irwin),and "Fundamentals of Private Pensions" (part of a series published/sponsored by the Wharton School).
4. There are several CD-ROMs that are excellent research sources. Try RIA, CCH, BNA, Spencers, etc. In our office, we have 2: the BNA research service (includes IRC, regs, DOL, PBGC, relevant court cases, etc. Very good.) and a CD of all (or most) of the Panel books (Pension Answer Book, 401k Answer Book, etc. Also good.)

You might also want to consider Sal Tripodi's The ERISA Outline Book. It is extremely thorough and detailed. We use it all the time.

The ERISA Outline Book and other reference materials are available from ASPA. Call them at 703 516-9300 or check their web site for their catalog.

While it focuses on one narrow topic, I do consider the book "Who's the Employer?" by S. Derring Watson, Esq. a "must have." He does the Q&A column under the same title.