This is an excellent web sites that provides handy calculations for almost all scientific and engineering disciplines. please use and spread for making things done by all engineers and others.

Mechanical Engineers:

http://www.mechengcalculations.com/index.html

Chemical engineers

http://www.mycalculations.com/chem/index.html

Civil engineers

http://www.civilengcalculations.com/index.html

petroleum engineers

http://www.peteng.com/

There is some speciality for every engineer, like civil engineer he has to check the strength of the brick or block as how much strength it is going to with standard also he has to check the fluid dynamics and coming to mechanical engineer he has to design the components and type of material used to resist the creep and fatigues on the load test which we are using so many softwares i CAD/CM packages in day to day with latest versions and coming to chemical engineers, The above links is very helpful to each and every one.