Scratch: We have previously waxed rhapsodic about all the great note-taking apps for iOS, and Karbon Works's $3 Scratch app for iPhone appears to be another interesting entry. It's designed to be a "quick-input" note-taker somewhat like iOS's own Notes app, but with some additions to make it even handier: Users can export their notes to Dropbox, iMessage, or even Twitter; notes can even be appended to existing Dropbox files. And folks who write for the Web even have access to Markdown formatting within the app. Scratch also lets you customize your keyboard with just the tools and buttons that you use the most.
Twist: Location-sharing social networking apps have gotten a bit of a bad rap lately, because they seemingly make it easy for unwanted strangers to follow your activities. The free Twist app for iPhone solves those issues by giving users more control, both over what location-based information they're broadcasting, and to whom. Enter an appointment into the app, and it will remind you when to leave--a reminder based on live traffic conditions at the time of your departure. While you can post the data to Facebook and Twitter, the app will also simply send messages with an estimated time of arrival to the person you're supposed to meet.
Vyclone: You've probably heard of "crowdsourcing" by now, the idea that information and art can be created by many dispersed people contributing to a single whole. Now that idea is being used to create videos, using the free Vyclone app for iPhone. The app encourages multiple users to take video of an event, and, after a few minutes, combines those videos into a single movie. (You'll still get to keep your raw footage, if you prefer it to Vyclone's creation.) Finished movies can be shared with friends, and users can even create "director's cuts" if they so desire.
Wikiweb: You might wonder why you need a Wikipedia app for your iPhone or iPad--Wikipedia is pretty accessible on your device's browser, after all. But the $5 Wikiweb app does two things that might make it worth your dough: First, it makes the spartan Wikipedia page look a little cooler, offering entries in a swipeable, typeset format for casual perusing. But if aesthetics don't matter to you and information is all you want, the app also helps you create custom "webs" of articles--useful if you're doing research--and share those webs via email or Twitter.