Each time you create a new post it shows a list of possible pingback enabled blogs with relevant contents to your blog entry. You can then choose ones
Deep link engine is a plugin that searches your post context for tags, using Yahoo or TagTheNet, those tags are used to search the blog sphere (via Google) to find relevant blogs and finally make pingback post to them. The whole process can be done automatically for multiple blog posts you have or manually on one post basis. Plugin does save the information it finds to its internal tables.