Information about gas compressors:
Links to vendor product pages and interesting links.

Compressor Performance Calculator:
Calculate your compressor polytropic efficiency and head for given inlet and outlet conditions.

Compressor Selection Tool:
Evaluate the different HC compressor technologies for given inlet and outlet conditions.

Centrifugal Compressor Map Predictor:
For given conditions, draw a centrifugal compressor map. Quick and usefull at early design stage.

PipeFlowCalculation.com:
Plenty of tools for pipe calculations: Control valve, flow orifice, venturi, pressure drop, pipe diameter. Requires Java.

Forcast date calculation:
For a given target date, calculates back or ahead.