Tagging people on blog entries and being able to access their profiles from tags
You can achieve that using the Mentions module 


  The Mentions module offers Twitter like functionality, recording all references to a user's username - using the [@username] or [@#uid] filter format - from various locations, providing a centralized page to track all mentions (via the Views module).


This module provides a configuration page, through that you can define the mentions pattern, and path (supports tokens)