Amazon Cloud Reader
Amazon Cloud Reader is Kindle for your web-browser, and it performs the task beautifully. Use it when you're away from your iPad or iPhone, and then when you leave your computer, pick up right where you left off on your mobile device.

Pandora
Pandora might be a little obvious, but amongst apps for streaming music, it's certainly our favorite. Pair this app with your iTunes library and Spotify, and all your auditory needs will be satisfied.

Aviary Image Editor
Aviary is an incredibly powerful image editing tool that mimics the functionality of Adobe Photoshop. It even uses layers and lets you save your image to your desktop afterward.

Feedly
Feedly is a clean reader for your Google RSS feeds. It both syncs your feeds and lets you edit them.

Audiotool
Whether or not you're a musician, Audiotool puts music creation at your fingertips. This full-featured web app lets you create beats and mix loops with its on-board mixer. It's a beautiful app, though at times it does load a little slowly.

Gojee
Gojee is an interactive cookbook that suggests recipes based on what you have in stocked in your kitchen, and from what you might be craving. The user interface is stunning with all of its high resolution images.

Pixlr-o-matic
Like iPhone apps like Hipstamatic and Instagram? Pixlr-o-matic brings that functionality to your browser, with an array of vintage effects for your photos, plus the ability to add effects like light leaks to your photos and vintage frames.

Tweetdeck
You might already be familiar with Tweetdeck as an iOS and desktop Twitter client. The web app is just as good, connecting you to Twitter, Facebook, and even LinkedIn. And, since it's a browser app and not an Adobe Air application, you don't have to worry about it crashing.

Weatherbug
Weatherbug is a simple but visually effective weather viewer for your browser, with some of the same features that's made the iOS app so very popular.

Simplenote
There are lots of web apps for taking notes, but Simplenote is hands down our favorite. It's nicely laid out, free, and syncs with both our iOS devices and Macs (via Notational Velocity). If you're looking for a simple note-taking platform, be sure to check this one out.