Filter Calculator (and other calculators)

When designing a simple Sallen-Key active filter yesterday for my VLF receiver I found several useful web resources. One of the best is http://www.calculatoredge.com/index.htm#electronics that has a lot of useful calculators for electronics. I like the fact that when designing filters it asks you, and gives you, values in "real" numbers like nF and kohms. Some calculators ask you to give values in Farads and ohms to the power E-09 and similar and are obviously written by a college professor and not a real engineer who finds it hard to work these out!