http://drizzle.org/
I've been following this for over a year and I've mentioned it here a few times. Drizzle is not like other projects (like PostgreSQL) in that it is forked from MySQL and seeks to maintain compatibility with MySQL. Basically, the Drizzle project tore MySQL down to its base code and kept it there. Several key features are
- Plugin based. No more are things built into the core. Want a new feature? Build a plugin
- Native multi-core support (this is a feature of MySQL 5.5 as well)
- Better memory handling
- Vastly improved replication (with native and plugins to choose from)
- Too many other differences to list here
Some more good news is that they are making their builds available via their own yum channel so we don't need the atomic-bleeding builds Scott had talked about before.
I predict that within 5 years MySQL will be mostly replaced with Drizzle. It won't happen overnight (even I can't migrate yet but I am testing) but it will happen as people get tired of MySQL and realize that Drizzle is where the community has moved.