[fjtorres]

The closest you'll find to OI is the Pocketbook line, as they are Linux-based and run both FBreader and Coolreader 3, offer Adobe DRM support, and handle a few other doc types; rtf, html, doc, djvu, pdf... Book organization is dual, as it has both a folder-based bookshelf as well as an abstract, links-based customizable structure under Favorites. Both offer up text lists, thumbnail lists, and cover grid, as well as a search system. Dictionaries are available from most of the reading apps, plus the gui can be customized via themes. There is a readily available, though not throughly documented sdk, and several dozen user developed apps ranging from coolreader3 and a juiced-up FBreader to educational flash cards, to games. There is a killer chess game, sudoku, checkers, etc.
I favor the 5in PB360 for portability (it is exactly the size of a CD jewel case and comes with a hard plastic snap-on cover) but they also offer models in the six and ten inch range, some with pen-based interface.
If you have access to the Nook STR, it can be rooted to access its broader android capabilities and run FBreader and Coolreader3 as well as Kindle, Overdrive, Aldiko, and a variety of pdf viewers.
Other readers offer very good reading experiences but if you want something OI-like, but with enhancements, you probably want to look at those two options first.

Edit: all that refers to eink readers.
If you don't mind giving up the extreme battery life and a bit of extra weight to go with LCD, pretty much any android 2.1 or higher tablet will get you there and Aldiko 2.x will likely be your app of choice.