It sounds like you're talking about regular keyword search results as opposed to the "7-pack" of local search results that can appear within keyword search under Google's Universal Search. It also does not sound like you're talking about rankings within Google Maps itself.
Perhaps your site was impacted by the "Mayday Update" which many have identified, which resulted in a loss of rankings for long-tail queries for some sites which Google deemed of "lower quality":
Penalizations can occur across an entire region/category of business as Google does its policing. For instance, if listings for a particular service in a particular city have become rife with spam, Google Maps could clean them all up at once.
The prime reason I assumed that you were NOT talking about the 7pack was that you mentioned "blogspot" -- Blogspot blogs typically are not showing up at all in Google Maps nor the associated 7pack.
[edited by: inbound at 10:11 pm (utc) on Jun 28, 2010] [edit reason] Removed Specifics/Request for specifics [/edit]