The disk defragmentation software for WHS is coming thick and fast. Raxco have now announced PerfectDisk 8.0 for WHS, see here: http://www.raxco.com/products/PerfectDisk2k/PerfectDisk_Home_Server.cfm.
A single copy of PerfectDisk 8 for Windows Home Server is priced at just $39.99, and also includes a copy of PerfectDisk 8 Professional for one of your networked PCs. A home site license is also available for just $99.99, and provides a single license of PerfectDisk 8 for Windows Home Server and up to 5 licenses of PerfectDisk 8 Professional.
There is also a free evaluation copy you can download and play with.