I had to setup Dropbox on PC-BSD for my wife this weekend, and discovered that it is extremely easy to setup and get working. Because of the popularity of this software (and the lack of a native FreeBSD port), I decided to post the instructions for how to get Dropbox working on your system in less than 10 minutes.
1) Install the PBI for "Wine" (or "Wine64" if using a 64 bit system)
2) Download the windows version of Dropbox from their main website.
3) Double-click on the downloaded file to perform the installation (I just used all the defaults)
1) Start the Dropbox program (from either the desktop or menu icons) and enter your login information to get it running.
2) It will automatically open the Wine Explorer to the Dropbox directory, just close this window. If you try to open files from this window, it will complain about not finding the necessary applications to read the file.
3) Just open up the "Dropbox" folder in your home directory instead (with whatever file manager you currently are using in PC-BSD). This folder is the one that Dropbox will manage and synchronize, so if you add/change files here, it will automatically be changed everywhere else you access your Dropbox account from.
I hope this helps! Let me know if you have any questions!