Anyone here have a recommendation on a good mountain bike?

Justin and I are looking at spending in the $300 to $600 range (per bike) for mountain bikes for both of us.
We plan on buying them locally, since it'll be our first bikes since our adolescent years, and we want to get the proper sizing. But as with everything, we like to get recommendations and do research so we're informed consumers regardless of where and how we buy.
I know some of the brand names of the higher end equipment, but am not interested in spending much outside our per bike price range, so no Trek Ironman's for us!
