The cool Sony e-book viewer Librie is available with English OS from Dynamism.

The Sony Librie showed up in Japan in early 2004.

The Librie uses its own file format, but is capable of displaying (converted) PDF files.
MAKE Magazine is also working apparently on some firmware hacks for the Sony Librie.

Dynamism sells the english OS Sony Librie for $479.00. The Librie ships with an English OS, as well as instructions for converting PDFs to Librie-compatible files.

Sony Librie Specifications:
Display panel E INK system electronic paper
Resolution SVGA (800×600 dot), approximately 170ppi (Pixels Per Inch)
Display color 4 gradation grey scales, black and white
Interface Memory stick lot, USB terminal and headphone terminal
Copyright protection OpenMG
Other functions Dictionary search function, audio correspondence (speaker and headphone terminal) Power source Single 4 shape alkaline dry cells (4), AC adapter
Built-in memory 10MB
Size W 4.96 in × h 7.48 in × d 0.51 in 126mm x 13mm x 190mm
Base machine mass 0.42lbs/190g
Main accessories Soft cover, USB cable and AC adapter