A while ago I stumbled upon a link on DRAWN, very briefly explaining how to copy your Photoshop presets to Dropbox in order to automatically backup, or even synchronize them with a second computer, e.g. your home. However, the original article is suggesting to use the Presets folder in the Photoshop application directory, which is simply not correct. Photoshop saves user created content (such as your Brush Presets) in the user’s Library, as shown below.
Furthermore, this neat trick isn’t specific to Photoshop and works with other applications, too! For example, I’ve applied this method to Corel Painter X without problems.
Alright? Let’s get started! Please close Painter/Photoshop and consider making a backup! I am not responsible, if you accidentally delete all your precious settings!

1) If you are using OSX Lion (10.7 or later) you might want to unhide your user’s Library first, else you won’t be able to locate your presets via Finder as easily. Open Terminal and enter the following:

chflags nohidden ~/Library/

2) Open Finder and copy your application presets into your Dropbox directory, e.g. /Dropbox/PROGRAM_NAME/Presets.

Photoshop CS5.1
/VOLUMENAME/Users/USERNAME/Library/Application Support/Adobe/Adobe Photoshop CS5.1/Presets

Painter X
/VOLUMENAME/Users/USERNAME/Library/Application Support/Corel/Painter X/WORKSPACENAME

3) Switch to Terminal and enter the following: “ln -s “, then drag and drop the folder /Dropbox/PROGRAM_NAME/Presets into the Terminal window, which will spell out the file-path to this folder. Hit Enter and Terminal will create a symbolic link to this folder in your user directory, e.g. /VOLUMENAME/Users/USERNAME/Presets.

ln -s /Users/YOUR_USERNAME/Dropbox/PROGRAM_NAME/Presets

4) Switch back to Finder and replace your original application presets folder (see 2)) with the symbolic link. Done!

Please check, if your symbolic link is successfully showing your presets! Clicking on the symbolic link should show the original folder’s data files! If you want to sync your application presets repeat the steps 3) and 4) at another computer, and be careful not to delete/overwrite existing presets within Dropbox.