Well, Solr is not technically supported by Engine Yard, but we do have a cookbook you can use to get started. Check out our help doc on using Custom Chef Recipes if they're new to you.
The cookbook will install 1.3.0 or 1.4.1 by default. It may require a small amount of tinkering to install a different version, but should be fairly trivial.
The recipe will configure Monit to keep an eye on Solr and will install it on Solo or Utility instances by default - We definitely recommend running Solr on it's own Utility instance.
Hopefully that'll give you enough information to get started, but do let us know if there is anything else you need or if someone else has a question or helpful hint!
John Yerhot, US Support Manager