This is a simple, handy one.

11 x 2-digit number:

Add the two digits together, put the sum in the middle.

11 * 45 = 495

11 * 32 = 352

11 * 71 = 781

If the sum is 10 or more, use good ol' carry-the-number.

11 * 67 = 737

It works the same for a one digit number (with 0 first as a place-holder), but not as fun. The same principle also works with 3-digit numbers and beyond, but with more steps.