Here is a tool that I created (in C#.Net) which comes in handy when dealing with multi-frame TIFF images.
It can be used to combine multiple TIFF files (multi-frame or single-frame) into a single multi-frame TIFF file, or split a single multi-frame TIFF file into many single frame TIFF files. To make it easier to use, I have created both a Windows and command line utility. The command line utility can be used for batch conversion. For downloads and instructions, please take a look at this page for more details.