The feed links are present in the page header so you can just point your feed reader to those pages to subscribe. The home page also has the feed links to those pages in the header.
|Page||Atom feed||JSON feed|
I have dedicated (and hidden) pages for both blog tags and project tags.
To subscribe to them, just click on the tag you want and point your feed reader there.
The tag feeds follow the structure
At the moment, you won't be able to subscribe to the same tag on both blog and project using the same feed, I may not add this feature at all as I don't see why anyone would want this.