I've been seeing a lot of good stuff about PocketBook. They support all major ebook formats. They're also good if you're privacy focused, though it comes at a price. Their privacy policy makes them the only brand I'd ever consider. Here's a few links depending on your needs and budget:

• Basic Lux 4 has a 6" monochrome display. This is their cheapest option.
• InkPad lite is their biggest display at 9.7". An all-around solid, affordable option from them.
• Era is a 7" monochrome display. I'm drawn to this one due to the functional bezel.
• InkPad color 2 is a 7.8" color display. One of their most expensive options.