The easiest way to contribute to IMathAS is to use it! By reporting bugs to the support forum, problems can be fixed. If you feel a feature is missing, request it. If it fits with the mission of IMathAS and would be useful to other people, every effort will be made to add it.
If you begin writing IMathAS questions, consider contributing them to the user community by adding them to the question libraries on imathas.com. Also, if you write question macros that add features that others might find useful, please consider contributing them to the project.
Tell your colleagues about IMathAS!
Visit the services page to look over services that will contribute funds to the IMathAS project. Got an upgrade you want now? Consider commissioning it. Buying a service is also a great way to justify to your finance department a contribution to IMathAS :-)
If you have more money than time to spare (lucky you!), you are welcome to donate funds to the IMathAS project. You can either donate directly to me (no, I'm not a non-profit organization; no tax write-off, sorry!), or if you prefer, you can donate directly to my web hosting costs for running imathas.com.