How do I move a file (or folder) from one folder to another in TortoiseSVN?

svn move — Move a file or directory.

http://svnbook.red-bean.com/en/1.0/re18.html

In Windows Explorer, with the right-mouse button, click and drag the file from where it is to where you want it. Upon releasing the right-mouse button, you will see a context menu with options such as "SVN Move versioned file here".

http://tortoisesvn.net/most-forgotten-feature

To move a file or set of files using Tortoise SVN, right-click-and-drag the target files to their destination and release the right mouse button. The popup menu will have a SVN move versioned files here option.

Note that the destination folder must have already been added to the repository for the SVN move versioned files here option to appear.