Epiware is an AJAX project and document management software which have been recently released, written fully in PHP. THe Libary section is very heavily AJXAJED, and accomplishes the following :

-Can drag and Drop files between folders
(Permissions are applied, so cannot drop in folders do not have write access etc..)
-There is a SHFT-CLK as well as CTRL-Click functionality for select
-Right click Dropdown menu. (or drop-down arrow for those not aware of right click)
-File edit and movement history,
-File access history,
-File Blog
-Check-in Check-out capability
-Watch Folder and File features,
-Text is extracted from both PDF and Word files so can be indexed.
(Can search on content of WORD and PDF files)
-TrashCan, etc....
-and works in both IE and Firefox
- 100% Free for Non-Profit and Educational

Epiware is available for free for educational purpose, commercial license starts from $1000 the 50 users. The web DMS solution is very interesting as it could be easily integrated with other projects in addition to its great AJAX features which make it very easy to use. There is demo and downloads available on the website, you can find also more information about the product and pricing ...etc.