synthesizers.com has a beta modular planner similar to the
Mega Eurorack Modular Planner. You can
find it here. The following are some specs and requirements.
Features
* Easy to learn and fun to use
* Select from any style of cabinet, up to 9 per system
* Drag and drop modules into cabinets effortlessly
* Add controllers, patch cords, etc.
* View front or back of cabinets
* Show modules as pictures or as function text
* Automatically totals price as you add/remove products
* Automatically adds power components if desired
* Calculates power supply and consumption
* Save and recall system configurations
* Start with a standard system or create your own from scratch
* Produces a complete product listing with pricing and shipping weight
* Creates a web page (HTML) of your custom system
* Exports product listing to a spreadsheet program

System Requirements
* The current version of SynthInvent runs on a Windows PC running XP
* SynthInvent will probably run on Vista, 98, ME, 2000 also
* Your monitor must be at least 1024 pixels wide
* A mouse or other pointing device
* Microsoft .Net framework V2 (Already on many modern Windows computers)
* 2 MB hard disk space"