Here are a lot of Sudoku problems and solutions plus a general solver program that you can download.
One novel feature is the addition of some simple problems suitable for kids. These are all smaller than the standard 9X9 geometries and include 4X4, 6X6, 8X8. A couple of examples are shown below.
There is also an archive of some problems I created earlier. Most of these use different geometries from the usual 9X9 problems which makes solving them more engrossing. An example is the toroidal problem, illustrated below, Here the overall grid is still 9X9 but whereas the normal problem contains 9 3X3 square boxes where a number may not repeat, in the toroidal problem these boxes are replaced by helices which wrap around the problem. The same problem is shown twice, once as it would normally appear and secondly with each stripe shaded a different colur to highlight the effect.If you follow one of the holices you may go off the left hand side only to reappear at the right, similarly for top and bottom. Hence the overall geometry is doughnut shaped (toroidal).
This whole exercise started with a Sudoku solver program I wrote as an interesting challenge. I believe this is sufficiently general that it can solve any Sudoku problem of any shape of size. It can certainly solve all those in this web site.
There is an explanation of the program, plus I can send a copy to anyone who wants to try it out. Just leave a comment with your email address.
I have also used this web site as a store for the context sensitive help pages.So there are pictures of most of the screens.