I'm using Aaron Schaefer's Optimal title wordpress plugin to modify the way wordpress displays the title by default. This plugin provides a function similar to wp_title() but your title will not contain "blog archive" in front of your post's title and this is good for seo.
You will have to modify your header template and replace the call to wp_title with a call to optimal_header().
In a previous post I presented a plugin for integrating Jerome's keywords plugin with google sitemaps, this post will show you how to integrate it with the optimal title plugin.
I had to modify a the optimal_header function a bit because I use Jeorme's keywords plugin for tagging and I wanted the tag to be included in the title for better search engine indexing. I had to add the next piece of code right before the return from the optimal_title() function ( in optimal_title.php ) , actually before the line "// send out the generated optimal title accordingly" :
if(function_exists('is_keyword') && is_keyword())
$optimal_title=get_the_search_keytag()." $sep ".$optimal_title;
Now the title of a tag page looks like "tag_name | PatchLog"
What do you use for seo on your blog ? Please me know in the comments.