468 x 60 pixels - Full Banner. The most common banner size on the internet.

180 x 150 pixels - Rectangle.

234 x 60 pixels - Half Banner.

125 x 125 pixels
Square Button.

120x90 pixels
Button.

126 x 60 pixels
Button.

88 x 30 pixels
Small Button.

240 x 400 - Vertical Rectangle.

300 x 250 - Medium Rectangle.

336 x 280 - Large Rectangle.

250 x 250 - Square (maybe a pop up).

90 x 600
Narrow
Skyscraper.

120 x 600
Regular
Skysraper.

160 x 600
Wide
Skysraper.