dminor 

K2s are, for the most part, solid values in an entry-level pricepoint. They are Taiwanese-manufacture frame (what isn't these days?) imported and assembled by K2 (the ski folks) headquartered on Vashon Island right here in the state of Washington. Their lower-end full-suspension stuff has been suspect in the past (almost department-store-ey sometimes) but their hardtails have been OK values (and some downright burly - -like the old Brass Monkies) REI carries them a lot (another Washiington-based company)

Iron Horse is another price-pointed brand that is hit-and-miss depending on whether it is sold in a big-box store or a local bike shop. Iron Horse is headquartered on the East Coast and that does make a difference depending on where you are; IHs tend to be set up (geometry-wise,etc.) more suited to their native East Coast (tight woods, lots of rooty, rocky trails, etc.), whereas K2s, etc. seem to be more West-coast riding-style oriented (a bit more wide-open, slacker geometry type preferences). It may depend to some degree on where you are located which might more generally suit your particular needs.

I've spoken in a lot of generics but I hope this helps some anyway. Other people can probably fill in the blanks with more specifics.