This is an interactive Java applet to solve the 6 x 10 rectangle problem. Here is another applet.

Here are solutions to all the rectangle problems.

Solutions to several problems, including the triplication problems (scroll down the page to see these), are given here.

Several interesting short articles may be found at the bottom of this page.

Here a link describing computer algorithms to solve pentomino problems.

There are many other sites which may be found by searching the internet. Feel free to explore!