We've seen Google testing a number of different display elements in AdWords over the last few weeks.
Google is pulling store ratings from Google Products and displaying the aggregate rating inline with ads. Below are the display treatments for the top and right rail ads returned for a search for 'grills':
Condensed Site Links
Sitelinks within ads have been available to advertisers since late 2009.
We've begun to see Google test 'condensed site links'. These site links take up much less real estate, but they also are appearing on a wider variety of search terms. The example below was from a search for 'www.cheaptickets.com'. You'll see that the condensed site links are for a competitive advertisement from SmartFares.
Previously reported at SearchEngineLand, we've seen Google testing related ads the longest. We've only seen the ads on the right rail, and they only appear on search terms that don't have many existing ads (eg there was whitespace before).
We've seen related ads appear extensively on branded search terms. For example, these two 'Related ads' appeared on a search for Mandalay Bay:
This ad format will be a particularly interesting one to keep an eye on. They are effectively 'broad broad matched' ads. In many cases, the advertiser may have had no intent of appearing on a branded search term. I expect many large brands would be unhappy to see their clean search results suddenly occupied by competitive advertisements that were placed through no direct action of the advertiser.
This test has run long enough and is widespread enough that I would be surprised if it doesn't become an AdWords 'feature'.