People Software have developed several online applications for our business including our CRM, Project Management, Staffing, HRIS, etc. The support has been excellent and they work with us to ensure that we are able to use their tools to the best of our ability. It's a bit expensive compared to some other vendors out there but it is worth the cost.
If you're looking to develop an application for your own use or to offer as a Service to clients - I would definitely recommend People Software toโฆ