You can link directly to the free
SOLO on
Simon Tatham's Portable Puzzle Collection. Probably better if you saved the file to your own server. It's a very simple program. No bells or whistles as far as solving. Some people will not want to run an EXE file.
These sites will give you a few lines of code to copy and paste into your webpage, automatically loading their daily puzzle to your page:
http://www.dailysudoku.com/sudoku/syndicate.shtmlhttp://www.sudokuhints.com/It's not exactly what you asked for, as they aren't generators, but they are free, but they hope to drive traffic to their pages. I've others that offer the same or nearly the same feature.