Mindscape certainly pumped out a large quantity of games for the NES, but most of them weren't of great quality:
Days of Thunder
Flight of the Intruder
Indiana Jones Temple of Doom
Mario Is Missing
Mario Time Machine
Notables: Most of these games can be passed over and you wouldn't be missing anything. Their best stuff is the Atari arcade games they licensed for the NES. Battleship is a decent take on the board game, except they forgot to add in a 2 player mode. M.U.L.E. is a VERY bizarre and original NES game, and I wouldn't hesitate to recommend it (I believe it had origins on the PC). Conan, Infiltrator, and The Last Starfighter are all wretched piles of crap that should star far from your NES.
Mindscape helped to release the ambitious Miracle Piano set, which included a NES cartridge and an actual keyboard. By hooking it up to the NES and following the instructions on the cartridge, people could learn how to play the keyboard. Unfortunately, sales flopped, and now this is a hard to find accessory.
Status: Mindscape is now owned by Mattel Interactive and it would be hard to say whether any of the original workers are still there or not. Mattel Interactive makes a lot of crap GameBoy Color games based on their properties such as Barbie and Hot Wheels.
Best Titles: Paperboy 1 and Road Blasters really stand the test of time. M.U.L.E. and Gauntlet 2 are good 4-player games.
Popularity of Games: Average
Rarity of Games: Average (both Alfred Chicken and the Miracle Piano cart will pose a challenge)
Overall Rating: C
Website: http://www.mindscape.com (links to Mattel Interactive's online store)