I've written an example SDL/OpenGL program which illustrates the following:

1) Very basic multitexturing
2) A simple OpenGL screenshot technique
3) Loading and saving TGA files

Feel free to download the source code:

multitex.tar.gz (98.4 KB)

As usual, no new ideas here, just the results of my feeble experimentation. Only tested with FreePascal on Linux (fpc -Mobjfpc multitex.pp). Will probably require small changes to work on other platforms and Delphi compiler.