I had the same need and first tried out Titanium Media Sync (on HTC Desire) but was annoyed to learn that you only have limited options for the sync (currently "continuous" and "single one way"). I needed the app to upload (and unload) photos and videos from the device to a network location, ultimately to free up space on the device. However, with the continous sync, any files deleted on the device will result in deletion on the network as well; which does not provide much of a backup.
I ended up with Syncness, which is exactly what I needed. You can configure it to sync only with specific networks, at specific hours of the day, only at A/C power, etc. (the latter is in all fairness also supported by Titanium). It can even save original file dates/info to the remote location. You can also ask the app to delete the synced files once they have been copied to the remote location. Syncness ftp's the files to my Synology FileStation NAS server on my home network - I'm not sure what other transfer protocols are supported.
/Jakob