Just came across this nice overview by Rudi Grobler, a developer and community guy from South Africa I had the chance to meet last year.
Rudi lists five very good toolkits including WP7 Contrib and the not to miss Silverlight for Windows Phone Toolkit.
I’d like to add MVVM Light Toolkit and ReactiveUI.
Note: WP7 Contrib already contains MVVM Light Toolkit integrated but you can also use it on its own.
Direct link to Rudi’s blog post: http://www.rudigrobler.net/blog/windows-phone-7-must-have-toolkits
‘Quick tip’ posts are short, useful posts pointing to content and tricks that might otherwise go lost in a typical 140 chars message on Twitterverse.