Over the past year or so, Google have been increasing the number of formats of AdWords banner ad sizes that are available for customers to use.
Unusually for Google, they have been fairly quiet about advertising this fact.
At the time of writing this, the following sizes are available:
When you are having display ads created, it is imperative that you get as many of these variations created as possible. You could well be missing out on an effective placement because you don’t have any ads that are able to fit the slots they have available.
An up to date list of ad formats, requirements and policies can be found in the Google AdWords support documentation:
Remember to try and use animation where possible, as the intention of your ad is to draw the readers attention to your ad after all.