http://www.thetimmys.com/flash/picross/
It's a remake of the old gameboy game Picross, realllly addicting.
To play simple shade in the correct squares. The numbers in the rows and columns give hints as to how many squares in a row are shaded for that particular row or column.
Example: The number 15 means that all 15 squares are shaded, but a number series like 7 2 would mean that somewhere on that column/row 7 squares in a row are shaded, then somewhere after those 7 there are 2 more shaded squares.
The numbers are always in order so if you saw 1 3 4 the 1 shaded has to come first, followed by a series of 3 then the 4.
Enjoy.
Edit: Number 2 is a whole hell of a lot easier to start with than number 1.