RAID 5 URE Calculator
Found this today. This is a really handy tool for quickly getting URE risks with RAID 5. Sadly that's the only useful calculation on the site. RAID 6 and other levels are multiple risks layered on top of each other so nearly impossible to demonstrate easily.
If you combine the drive failure rate calculator for RAID 0 with the URE Risk of the RAID 5 calculator you can actually get some decent idea of total risk.