There are PDF slides and a video on youtube. But I wanted to put some of the links I used to gather information here, as an easy place for folks to come and click links if they like, or if they want to research on their own.
At the official Drizzle documentation:
What is Drizzle?
Drizzle differences compared to MySQL, including gotchas
MySQL Connect, Oracles business/technical conference for MySQL
Virtual Developer Days, March 12th and 19th
From the Percona website:
Percona 5.5 vs. MySQL 5.5 feature comparison
Percona Live, Perconas business/technical conferences for MySQL
Why Percona Live?
MariaDB vs. MySQL compatibility
What is in the different MariaDB Releases?
Tweet asking about making MariaDB 10, MariaDB 56
Whats in MariaDB 10
Hopefully the video gives a good overview; I know that many will learn a lot from this controversial video.