I came across this site that has several useful utilities for designing LPF and HPF filters.
LPF:
http://www.beis.de/Elektronik/Filter/ActiveLPFilter.html
HPF:
http://www.beis.de/Elektronik/Filter/ActiveHPFilter.html
Main site:
http://www.beis.de/Elektronik/Electronics.html
The default gain for each stage is unity but other gains may be selected.
I've found it useful in designing anti-alias filters for NBTV,
Regards,
Graham