Polar Instruments If you need to calculate impedance on a single or multilayer circuit board with multiple controlled impedances then you should check this software out. They are also the most popular impedance software that I have ever worked with.
UltraCAD Design Inc. These calculators can calculate the following types of impedances; microstrip, Embedded microstrip, stripline, Edge-coupled Stripline, and Broadside coupled stripline They also offer several freeware versions, check out their website for more info.
Skottans Elektronik This web site has calculators for Micro Strips, Embedded Micro strips, Strip Line, Differential Micro Strip, and Differential Strip Lines. Also have you wondered about Cross talk or Current Carrying Capacity? There are several calculator for that too. Best of all they are provided free online. Check out this site for more information.
