I'm starting my second semester as a CS Phd student and the volume of digital documents (usually PDFs) that I need to read is ever increasing. Extended reading on a PC hurts my eyes, so I've been printing them out, though this seems like such a waste. I'd really like a relatively cheap e-Paper-based reader that can render PDFs (or has a format that PDF can be converted to). I don't care about wireless connectivity, playing MP3's, purchasing digital books, or fancy touch-screens. Ideally, I'd like a simple device that I could plug into my PC over USB, copy some PDFs onto it, and read while away from the computer without wasting paper. Does such a wonderful device exist?

Most of the cost of the readers you're seeing now is the "e-ink" display. The price difference between the cheapest Sony Reader ($199) and the cheapest Kindle ($259) is very small.

There are some no-name ones as well, but it looks like they're only like $10 to $20 cheaper than the Sony Reader.

Check out the mobileread wiki to see which reader is right for your wallet.