I'm not sure I'd advocate using buildout for this, but as (you've probably seen) there are a few recipes for stuff like haproxy[ha], varnish[va], postgres[pg] and nginx[nx] available.

An example of how to combine many of these, for deploying a complex stack, could be:

http://www.martinaspeli.net/articles/an-uber-buildout-for-a-...

Another somewhat complex example:

https://github.com/kybi/buildout-openerp-postgres

You might also find this enlightening: http://glicksoftware.com/blog/using-haproxy-with-zope-via-bu...

[pg] https://github.com/securactive/sact.recipe.postgresql

[va] https://github.com/collective/plone.recipe.varnish

[ha] https://github.com/plone/plone.recipe.haproxy

[nx] https://github.com/collective/plone.recipe.varnish