I believe there are two new features now in Google Webmaster Tools. They are the ability to test sitemaps before submitting them to Google and testing crawlers specifically for Googlebot-Mobile.
Don't you hate it when you submit a sitemap to Google and you have to wait to see if there are issues with the sitemap file? Google now lets you test your sitemap files before submitting them!
Here is how it works, you go to Sitemaps under the Site Configuration link in Google Webmaster Tools. At the top right there is a new button that reads "Add/Test Sitemaps". Click on it and you can plug in a URL and then click on the "test sitemap" option:
Then Google will run the test:
When the test is complete, you can view the results:
And then here are the results:
This is incredibly useful!
Googlebot Mobile Crawler Test
Google also added to the Crawler Access a way to test your site with Googlebot-Mobile. I am not a 100% sure if this is new (I am told this actually isn't that new but they did add Googlebot-Mobile for Smartphone), but I am told it is:
New Design With More Details
Now statistics from Web, Videos, Images and News are featured prominently. This lets you see how many items of each type were submitted (if any), and for some content types, we also show how many items have been indexed. Sitemap errors and warnings are now grouped.
Forum discussion at Google Webmaster Help.