UltimateDefrag (Freeware Edition) is a Free Portable Defragmenter that "allows you to optimize your hard drive any way you want". This free defrag tool enables a user to not only defrag files on a disk, but also put frequently accessed files in areas on your hard drive where they will achieve maximum performance.
Defraggler Portable is a free file defragmentation tool that can be used to defragment only the files you want to or defrag an entire drive. It can be used for defragmenting both internal and external drives including USB flash drives.
PageDefrag is a free portable defragmenter that allows you to defragment files that you might otherwise be unable to defragment with typical defragmenting tools. Files such as registry, paging, event log and hibernation files or those that are open for exclusive access are just a few examples of what this
WinContig is a simple free defrag tool that can be used to quickly defragment files without defragmenting the entire disk. This tool can even defrag ISO files.
