Soft updates are some voodoo (note to self - learn how filesystems work) you can do to a FreeBSD3.x or later ufs partition to improve performance and reduce the risk of damaging your file system after a crash or power cycle.
Soft updates makes a distinction between writes to file, which will always be lost if you pull the power plug, and metadata operations - deleting, creating and moving files. These metadata operations are kept track of and written out in a fashion which protects the file system from such interruptions.

Howto:
Unmount your target filesystem. If you wish to work on the root, you'll need to drop to single user mode.
Now run tunefs -n enable /hello and remount the filesystem. (Where hello is your target filesystem)
To verify, run tunefs -p /hello .

I haven't tested it yet, as the power outage faeries haven't been round since yesterday, but I'm hoping that the fbsd box in the corner will take less than an hour to boot next time.