iPhone: Annotable is one of the best image annotation tools around, especially after Evernote abandoned Skitch a couple of years ago. Now, it's been updated with a slew of new features, making it much more versatile.

iOS: When it comes to adding annotations to images on iOS, what works best for you really depends on what you're trying to convey. If you're looking for a dead simple approach without a ton of flair, This by Tinrocket is an app that works well.

Chrome: It's not that difficult to download email attachments and add your notes to them, but wouldn't it be nice to review the attachment, add your feedback in-line, and send it back right inside of Gmail without even downloading the file first? Framebench can do that.

Android: Showing is sometimes better than telling, but why not do both when you can? Clarisketch lets you share a picture with drawn-on annotations, and it even includes your own descriptions as you say them.

If you're horrible with names, you know the embarrassment of forgetting who your neighbours are. Finer Things in Tech recommends using a maps app and the annotation app Skitch to keep track of those neighbour's names.

Mac/iOS: Evernote's simple image annotation tool, Skitch, received an update today. It adds two new annotation features that make it easier to quickly provide feedback.

Windows: Windows 7 shipped with a much-needed snipping tool for taking partial screenshots, but it's not exactly loaded with features. Snipping Tool++ adds a few handy features that connect your screenshots to the cloud.

Chrome: If you're trying to send someone to a specific passage of a large article, it's difficult to tell them exactly what you want them to see. Yellow Highlighter is a Chrome extension that lets you highlight text and send a link directly to it.

Mac OS X Leopard only: One of the built-in Mac utilities that got the most feature additions in Leopard—albeit pretty quietly—is Preview, the PDF and image viewer. We've already covered how you can do more with Preview in Leopard, but Mac OS X Hints points out another good one: image annotation. Add arrows and notes, or circle and outline areas of an image in Preview using the Annotation menu. (In Preview's View menu choose Customise Toolbar, then drag the Annotate menu onto the toolbar.) Then, when you're editing a non-PDF image in Preview, just select your annotation, and click and drag on the image itself. Handy, and no third-party software required. Annotate non-PDF images in 10.5's Preview

Add interactive comments to your YouTube videos with the new annotation feature. To annotate to any video you've uploaded, just head to your uploaded videos page and click the Edit annotations button. From there you can add comment boxes, speech bubbles, and even links to other content. The catch during the beta test is that annotated video only appears on videos playing directly on YouTube and not embedded on other sites, but you can get an idea of the possibilities by checking out this annotated video. YouTube isn't the first to introduce this sort of functionality, but you can bet you'll see a lot more annotated video now that they have. YouTube Video Annotations