I have some MapInfo TAB-file and I'd like to save spatial reference to .prj-file. How it can be done?
MapInfo comes bundled with Universal Translator which can be found under the Tools menu. It is an additional option so may not be installed but should be on your installation disc. This should create a .prj file, like in Uffe's answer.
If you are doing this regularly/in bulk you could make a MapBasic program to do it for you. The following command will show you the prj string for the last table to be opened. You could then either copy and paste the result into a file or work some more Mapbasic magic to make it do it for you.