Rand Fishkin , of SEOMoz, needs no introduction from me. Here are his favorites: *** Sure – here goes:

• http://www.davidmihm.com/local-search-ranking-factors.shtml from David Mihm
• http://www.seomoz.org/blog/the-world-series-spidering-problem from Will Critchlow
• http://paulgraham.com/cities.html by Paul Graham

Hope that helps! Rand