First of all thanks a lot for your good work !
I have an idea of plugin, it's actually a real need !
I would like to have filters on my blog for category and tags, so that when I choose a category, every other posts disappear.
I know many themes use that kind of filter for portfolios. But I want it for my blog posts.
I would like a special page where all of my posts are presented in a grid (or masonry), and filters at the top or on the side.
When you choose, let say, two categories and one tag, only the relevant posts are shown
But if shouldn't reload the page (maybe a "load more" buttons at the end of the page can help).
And for multisites, it can aggregate the posts from every other blogs from the network.
I think the best exemple I found (but not a wordpress install) is the famous hub of tuts+ :
I know it's a lot to ask ! haha !
ps: i found some free plugins on the Wordpress directory (exemple ) But it doesn't work the way I need it.