Sony MZ-R900. about $300, but worth every cent! sony have a couple of cheaper models, too. the R-900 is their top model. Panasonic, Sharp etc work well, but when it comes to MD's, Sony is qualitywise your best pick by far.
I bought a Sharp MD-MT15 (or is it an MT-MD15?). It is a great unit and was only $250 Canadian dollars. All the units work well. Sony has some nice ones, Sharp and Aiwa, JVC and Kenwood. I know the Sharps are shaped differently than the Sony's in general. Both both fit into pockets well.
For field recording portable minidiscs are the best choice in my opinion because of excellent sound quality, editing features, inexpensive discs, inexpensive machines, and durability.
