Blogger Gets AJAX API/CSE Search Box
The search box uses the linked CSE feature to search all the posts on your blog, everything you’ve ever linked to from your blog, and any sites listed in your blogroll or any other sidebar lists. Adding it is as easy as choosing the widget and adding it to your template, so check it out.
The search results appear on-page, without the page loading. They just push the blog post down. There are at least two tabs, one for results from your blog, one for sites linked to from your blog, and one each for every link list in your sidebar (like one for blogroll, one for favorite posts).