Windows Live Photo Gallery includes a lot of fantastic features and one need not learn complex image editing suites to play around with their images. There are some interesting and useful third party tools available for Windows Live Photo Gallery, that can increase user experience. You can add a few such tools from the More tools menu on the Create tab in Photo Gallery.
Photosynth takes your photos, mashes them together to recreate a 3D scene out of your pictures that anyone can view and move around in to enjoy the minute details of real world using features like zoom.
Download Tool: Photosynth.
Image Composite Editor
Image Composite Editor is an advanced panoramic image stitcher from Microsoft Research which provides a lot more control than the stitching engine inside Photo Gallery. The stitched panorama created using Image Composite Editor can be saved in High Definition and in a wide variety of formats, from common formats like JPEG and TIFF to multi-resolution tiled formats like HD View and Silverlight Deep Zoom.
Download tool: Image Composite Editor
Auto Collage is a tool from Microsoft Research that can be used to fuse & seamlessly combine images into a blended collage, preserving the spirit of an event or trip. The Advanced object selection and blending technologies in Auto Collage seamlessly combine the pieces from different images into a beautiful new AutoCollage.
More information and Download: Microsoft Auto Collage.
These add-ons easily integrate with Windows Live Photo Gallery programs and you can start doing more from Windows Live photo gallery immediately after.
Go here if you are looking for a video tutorial on how to edit photos with Windows Live Photo Gallery.