www.ik2nbu.com
Amitor Coil on Toroids SWL OM Antenna
Wire Horizontal Lops Magnetic Lop Antenna
ARRL Band Filters Coax Cable Traps
BEAMS ANTENNAS LC Parallel Calc
Rectangular Lops Tube P Greco
Helical Antenna Short vertical Antenna
Delta Lops Antenna RF SIM DESIGN
Load Vertical Quad Design
SPIRAL LOPS Vertical short Quarter
This is my  short list of preferred web calculators that i use frequently to make fast RF and simple on line circuit simulations:

http://www.changpuak.ch
http://coil32.net/online-calculators.html
http://www.claredot.net
http://tonnesoftware.com/index.html
http://www.daycounter.com/Calculators/

We can make a comparison between the calculators, to be sure of schematic RF values results, but littles differences are normal and  will be corrected during pratical construction.

You must consider almost a 5 % of tollerance in RF value and, above all, use only a right selection of electronic components.
I used this software programs for several goals: projects of circuits, filters calculator, differents design antennas etc. they are in Zip files and most of them have a help menu in English language, the old DOS version is ARRL free programs 90ys.
This software is easy to use and run also in WIN PC without trouble. You can also find simple Excell Calculator and in most programs you can print and save the results of calculation. The following links go directly to my public folders on G.Drive.