Mark Callaghan from Google on high availability MySQL.
OurDelta produces enhanced builds for MySQL, with OurDelta and third-party patches, for common production platforms. All the builds are freely available for download.
Percona builds binaries that contain recent versions of the MySQL database server, plus additional popular patches not included in the official binaries from MySQL/Sun. Hat tip Morgan Tocker.
Ultra Moneky is a load balancer similar to the likes of pound and haproxy. It allows multiple web servers to be seen as 1 by the client.
HAProxy is a TCP proxy / load balancer which will work for HTTP and a range of other applications. It advertises a small but expert user base and offers a range of very useful load balancing features. Apparently it competes with pound and ultramonkey.
Collectd is a simple, small utility to log system load every 10 seconds. It's written in C so it's not a script and offers good performance.
The Linux Virtual Server as an advanced load balancing solution can be used to build highly scalable and highly available network services, such as scalable web, cache, mail, ftp, media and VoIP services.
Linux HA produce the Hearbeat application which is used in high availability clusters.