Menu needs to be simplified and contextual: depending on which page you are, it should display
1. "Add a blog entry" as a link to a page with pre-filled values for course/module associations when appropriate.
2. Full-text search box filtered by the current context
3. Link to "Blog entries for this [site|course|module|group|user]"
No need for a search page, all blog pages are reached through links. Filtering is done by first reaching the page of the desired filter (site|course etc) then clicking the link in the blog menu block.
Once on the listing page, a tag cloud is displayed which makes it possible to filter the current selection of blog entries by tag.