Recently launched, minimalistic, and highly focused:

BrainStorm [] is an interesting tool written in Rails for web based collaboration. You can create Conversations and invite others to participate. It’s still a little bit buggy but quite interesting, since you can add a variety of content fragments – appointments, checklists, ideas, quotes, reminders, tasks, and so on:

Pixoh [] is an online photo editor. Currently it lets you resize, crop and rotate photos, but more features are on the roll.

ShortText [] lets you publish microchunks of text on the web. Each fragment gets its own (short) URL. Nice.

Last not least FeedSifter [] lets you create filtered feeds which only let pass items containing specified keywords. This is handy if you want to scan many feeds for specific topics only.