Nexus 7, Kindle Fire, (almost certainly) iPad Mini; it seems like you might need to add Nook to the bunch. A source at Digital Trends says there's a new Nook getting announced this month, and it might be a Windows 8 tab.
There's already evidence that suggests a new Nook is inbound. For one thing it's just been a while and this seems like the time to announce a new tablet, but there was also a Nook price-drop a while back. The next step—which you should keep your eyes open for—is when they inevitably go out of stock.
While the announcement is said to be later this month, the actually launch of the device isn't expected until later, late October perhaps. By that point, Windows 8 will have been released, and considering that Microsoft has been getting friendly with Barnes and Noble, Windows 8 might make sense.
So far, however, there's nothing but speculation, so the future of the Nook is far from set in stone. That said, it's hard to believe Barnes and Noble would miss out on this tablet-party, and Windows 8 could give them a unique edge. We'll have to wait and see. [Digital Trends via Tom's Hardware]