Ultimate Tag Warrior is a multi-headed hydra of a plugin. It allows you to add tags either through the Write Post page in wordpress in a tag box, on posts using an AJAXy box, and in posts using special syntax from external editors (or internally, if you’d like). From the write post page, you can also get suggestions for tags using the Yahoo! keyword suggestion service.Once you’ve got your tags entered; you enter a realm of interesting ways of doing things with your tags. At the complicated end, AJAXy search is included with the download (it may need some customisation to match your theme). At the simpler end, you can automagically have tags included at the top and bottom of your posts without making changes to themes.
Visit the support forum | View Installation, and basic usage docs here (it has links to further documentation…) | See themes, extensions and other hackery | UTW 2 stuff
If there are things missing from the documentation, please let me know!