Taking recommendations for good sync/backup program (other than Time Machine)

Question

Hello everyone,
I'm on the lookout for a good file synchronization program (other than Time Machine) which I can use to make one-way backups of specific subdirectories. The ideal program would do the following:
1) Do one-way synchronization of user-selectable subdirecotries within a directory A to directory B either on same hard drive or on external hard drive
2) Can be set up to make sure that B has the exact subdirectories/files as A, deleting any that are not present in A and adding anything that is added to A or anything that has been changed in A
3) Will not generate useless junk files that require me to manually clean up after them
4) Will not alter files and directories in A in any way
5) Will be inexpensive
6) Will not interfere with Time Machine, which I already use to backup multiple volumes to a single external hard drive.
I checked the App store first, but was disappointed that all three apps had mixed reviews, and none had recent reviews attesting to their efficacy (which I always interpret as a bad sign).
I also did a quick search for third-party programs, but their websites will only have good reviews, so naturally I'm checking here first.
Basically, I want this program so that I can use it to sychronize files to my Cloud (Box, Google Docs, Dropbox) directory to share with my friends, and also to make redundant backups of sensitive files to additional external hard drives not being utilized by Time Machine.
Any input would be greatly appreciated.

Answer 1

CCC can be set up to copy just selected directories, or the entire disk.  It does not need to make a full clone (although a full clone is a good way to have*something* that functions in case of emergency).
I take the approach of using a tool that can do much more than simple because it can do *that much more* in a pinch.
I gave my best advice, and have not investigated in more specialized tools.
Good luck to you.