OpenVPN Access Server ships with ucarp integration out of the box, and for the most part it just works. Keepalived is another common daemon for managing floating vips. If I understand correctly, ucarp was originally designed to support redundant routers and firewalls, but in my experience, they are great for moving vips between stateless services, like load balancers and reverse proxies.

Agreed. ucarp is almost trivial to deploy:

http://www.debian-administration.org/article/678/Virtual_IP_...