His contributions to the Monkees albums are always solid. Get the mono versions if you can. Also, a ton of Monkees stuff, including top notch Nesmith songs, showed up the collections "Missing Links, Vols. 1-3. You have to skip over some pretty godawful Davy stuff, but these Mike songs are killer.
As for post Monkees stuff, the three RCA albums with the First National Band are great. Loose Salute, Magnetic South, and Nevada Fighter are the titles. They all pop up on vinyl for reasonable prices. If you like country rock from that era, these are the cream of the crop.
I never checked out too much after these three, but a friend of mine swears by his concept album "The Prison."