Another Minneapolis hip hop label, much like Rhymesayers, is Doomtree.
Group of artists that all collaborate together. Ones I'd recommend are P.O.S, Sims and Cecil Otter. Sim's just released a new album. It's pretty sick, IMO.
By Atmosphere I'd say get the albums "Lucy Ford" and "God Loves Ugly." If you can learn to love those 2, you'll love everything sluggo does.