We created a group Tumblr page and tagged all the posts so we could search by topic. I can't seem to figure out how to do this just for our page. The tags are fairly common and pull up all kinds of posts from other blogs.
Every tag has two URLs that only show the posts on a specific Tumblr.
Let’s say the Tumblr is called
You could also search for the occurence of a string (which includes tags):
I'm sure this is probably common knowledge but just to update this:
If you're viewing your blog (called 'example') in dashboard mode (i.e., the address bar says "tumblr.com/blog/example") then when you click on a tag for the post (for example, the tag 'foo') it will pull up all of Tumblr's posts. The tag links in dashboard mode go to tumblr.com/tagged/foo.
By going to your actual blog page---"example.tumblr.com"---the tags clicked will pull up results within your blog, going directly to the URL "example.tumblr.com/tagged/foo".