b2evolution is now part of the PLESK Application pack (they wouldn't list the versions of their bundled software though :-/).

This comes in addition to:

• Fantastico for cPanel (not always up to date... but widely available: InMotion, WebHostingPad, etc...)

• SimpleScripts (my personal favorite installer -- available at HostMonster and BlueHost -- very well updated!)
• Installatron (well updated; I wish more hosts would use that one!)

So, if your web host does not provide 1 click install of b2evolution yet, or if it's an outdated version, feel free to tell them they are seriously slacking! :p