You can use all our AJAX controls in SharePoint 2007/2010 sites and the following articles from the online documentation illustrate how this can be done:
For RadTabStrip in particular, you may consider using the same approach presented in this topic
which explains how to replace the default Quick Launch Menu with our AJAX panelbar (reusing the same data source).
In addition to that, you can utilize the SharePoint 2010 web parts included in the Telerik SharePoint Acceleration Kit
(currently in CTP stage). I encourage you to try it out and share your feedback with regards to the components/features included in its present version.
the Telerik team