Best way to keep up on the newest YouTube videos by a certain user or a specific tag is to subscribe to the RSS feeds and watch them right on your Reader. I use Google Reader and for some reason there's no one-click subscription button to a user's videos. Or maybe I've missed it somehow. from YouTube:
RSS Feeds for Tags and Users
To create an RSS feed for your favorite tags or users, simply enter the tag or username as specified in the below URLs. You can then add this URL to your newsreader. Please note, you will need to create a feed for each individual tag or user you wish to subscribe to.
Tags: For example, if you wanted to create an RSS feed for the tag "monkey," you would enter: feed://www.youtube.com/rss/tag/monkey.rss
Users: feed://www.youtube.com/rss/user/[insert username here]/videos.rss For example, if you wanted to create an RSS feed for the user "YouTube," you would enter: feed://www.youtube.com/rss/user/youtube/videos.rss
So, mine is: feed://www.youtube.com/rss/user/emonome/videos.rss