The .gvfs is where network attached folders live. If you've used "Places/Connect to Server", or typed smb://server/share into Natuilus, that's where your network drive will "mount".
You need to exclude your .gvfs folder from your back up, unless you actually want your network drive and all its contents to be included in your back up.
Other places you should consider excluding :
~/.cache (this is also where Chromium puts its cache, if you use that instead of firefox)
Others to consider :
- if you use VirtualBox, your guest systems are likely stored in .VirtualBox. On the one hand, you'll want to back those up. On the other, they'll be huge, so maybe you should back them up separately from your generic home drive backup?
- if you use Dropbox, you'll probably not have much need to back that up! Exclude wherever you told Dropbox to put its folder.
Finally, you can do some of this analysis yourself! Go to your Applications menu and choose Accessories, then run "Disk Usage Analyser". Once it's running, press CTRL-S to start an analysis of your home folder, sorted by size.