iPhone/Android: Previously mentioned web service Springpad is a great web-based notebook and organiser, and even though they do have a mobile-optimised web page, their apps for iPhone and Android make it a much more compelling alternative to Evernote.
Android users will be especially excited about this release, considering the recent Evernote drama on Android—many users are completely unable to view notes on their Android phones, and Evernote hasn't yet released a fix (the issue has been there for over a month now). Now that Springpad has a native app, however, note taking, web clipping addicts are unlikely to miss Evernote. In fact, Springpad's mobile apps have a few features that even Evernote doesn't have.
Not only can you make quick text or photo notes with Springpad, the smartphone apps allow you to add products, businesses, events, and other items to your notebook by searching through categories, location, and even by scanning a bar code with your phone's camera. Everything you add immediately syncs back to your Springpad account, viewable from any web browser. Even if you're perfectly happy with Evernote, Springpad has matured to the point where it's definitely worth another look, especially now that it's available natively on two smartphone platforms. Even it's desktop experience has evolved, with its own app store and smart web clipper to truly make it a worthy competitor to other organising services.
Springpad is a free download for iPhone and Android devices.