Got a few good articles for your review:

The BCS for Local Search Engine Optimization by David Mihm, “A Look at Why InfoUSA, SuperPages, Acxiom, Localeze, Yelp and InsiderPages Are So Important in Local Search”

Small Business Link Building: Part A – Analysing Opportunities over at SEOmoz.

Winning the Local Search Battle by Gregg Stewart
Winning the Local Search Battle – Part 2 also by Gregg at SearchEngineWatch.  Some good stats and info.