I'm using
SyncBack, and loving it. Free, easy to set up and automate. Despite the name, it does backup as well (which is really just 1-way sync, anyway)
For those who prefer portable apps, you can use
uniextract to extract just the app files without installing it. I've had no issues running it like this so far.
And although this should be obvious, I'm going to preempt some complaints and state now that SyncBack
Freeware is the version you're looking for, so I hope not to see any posts about "WTF you talking about there's only a trial version, shareware FTL". If you don't see it, scroll down like all sensible users would (or just do a webpage search).