Google Reader is on its deathbed
Feedly's one of the best options who need one reader on all their devices. Feedly has finally rolled out its web-based reader
Digg's Reader hasn't come out quite yet, but so far it's looking mighty fine
Weird to see AOL popping back on the scene, but AOL Reader is stripped down, simple, and fast
NewsBlur's got a solid, Google Reader-esque web app you can try out on the spot if you hop over to their site. And, if you're a mobile user, it also has an Android app as well as iOS versions for the iPhone and iPad. Free accounts max out at 64 feeds, which won't be enough for a real power user, but a real, unlimited subscription is only $1 a month.
This basically is Google Reader; the interface is practically identically. And you can login right with your Google account import feeds that way, though The Old Reader claims it's flooded at the moment, and won't let you. The downside here is that there are no apps (yet) and social integration is only available by connecting through Facebook. But it's great as a bare-bones replacement for web-use.
NetVibes is a web reader with some powerful customization options. Like any good RSS reader, you can resort to a pure feed approach, but NetVibes also has a dashboard setting that allows you to create and organize "widgets" for specific feeds and folders and move them around. The downside is that there aren't any mobile apps, so you'll be tied to your computer.
While a mobile app an never fully fill the hole Google Reader leaves in your desktop browser, Flipboard (Android, iOS) is another great, magazine-like mobile option for folks whose feeds are image-heavy. It's so pretty you might just forgive it for not living on your laptop.
It's by no means a perfect replacement, but it might be able to fill part of the hole depending on your use-case. Twitter doesn't have an "unread" state, so it's only good for here-and-now developements, but many outlets user their Twitters a glorified RSS feeds anyway, and there's no shortage of mobiles apps, for now anyway. If you're a light RSS user, and a heavy Twitter user, you might be able to work something out. Maybe.