UPDATED again. 2nd time this year! Just keeps getting better.
Besides screen capture, you can record videos with it. And the latest version allows you to put text and arrows on those video captures.

And he is making this program Win 8 compatible.

I use this portable program everyday in some way: web work, as teaching tool, even when learning a new job to take notes. Buy a license once, keep program for a lifetime free upgrades. Best program purchase I have ever made and HIGHLY recommend it.
So tiny & portable,
I run it from my usb stick so that no matter which computer I am working on, I have use of this program!
http://www.faststone.org/FSCaptureDetail.htmCURRENT FEATURES:
A small handy Capture Panel that provides quick access to its capture tools and output options
Global hotkeys to activate screen capturing instantly
Capture windows, objects, menus, full screen, rectangular/freehand regions and scrolling windows/web pages
Capture multiple windows and objects including multi-level menus
Record screen activities including onscreen changes, speech from microphone, mouse movements and clicks into highly compressed video files (Windows Media Video format).
NEW: A built-in video editor allows you to draw annotations and add zoom effects to video files Options to specify output destination (internal editor, clipboard, file, printer ...)
Draw annotation objects such as texts, arrowed lines, highlights, watermarks, rectangles and circles
Apply effects such as drop-shadow, frame, torn-edge and fade-edge
Add image caption
Resize, crop, rotate, sharpen, brighten, adjust colors ...
Undo/Redo
Support external editors
Save in BMP, GIF, JPEG, PCX, PNG, TGA, TIFF and PDF formats
Acquire images from scanner
Convert images to multi-page PDF file
Send captured images by email
Send captured images to Word and PowerPoint documents
Send captured images to a Web (FTP) server
Screen Color Picker
Screen Magnifier
Screen Ruler
Support multiple monitors
Run when Windows starts (optional)
Minimize to System Tray area
Small footprint in memory
And many more ...