JShot is a free and multiplatform screen capture and uploader application which allows you to capture and annotate a part of your screen and share it via the Internet in one step. It lets you to upload screenshots to the Web or send to an Instant Messaging partner. JShot works on almost every operating system, no matter you are using Windows, Linux or Mac OS X. JShot is completely free to download and use for personal usage. 

Features: 

Capture a rectangular region, full screen or clipboard content 

Capture active window, taskbar, deskop, widget (Windows only) 

Upload via FTP, ImageShack, Skype, Twitter, Picasa 

Drawing various shapes, adding text to the picture 

Moving, resizing shapes and updating shape properties 

System tray launcher 

Context menu integration (Windows) 

Screenshot history 

Undo/Redo 

System wide keyboard shortcuts (Windows and Linux x86/x64) 

Auto Updater 

Compatible with Windows, Linux, Solaris, Mac OS X, etc. 

It is possible to extend the functionality of JShot by installing plugins.