ThreadWatcher lets you download all the images from a thread open in your browser, with a single command, preserving the original file-names. Watching a thread lets you keep track of interesting threads; Growl notifications will alert you to new posts and images. ThreadWatcher also lets you post replies to the threads that you are watching, without having to switch back to your browser.
Tag and rate images so you can always find them with Spotlight or any application that supports OpenMeta tags.
The image dumper lets you post a group of images to a board, and will automatically start new threads if your thread reaches the limit.
When watching threads, tabs allow you to keep track of many threads in a single window.
Applescript support means you can initiate a download without leaving your browser. Example scripts are available here.