I have developed an MS Access database for a company to track data in regards to production of a certain commodity. It has many many tables, forms, reports, etc. These were all done as the user requested, and resemble the users previously used system, mostly printed worksheets and excel workbooks. This has created a central location for all information and has allowed the company to compare data in a new way. I am now looking to do this for other companies, but would like to switch it to a web application.

Here is my question. What is the best way to create unique solutions for individual companies that can have around 100 users each?

I would love to create one site that would serve all parties, but that would ruin the customizable nature of what I am developing. I love the ability to create reports, excel sheets, pdf, graphs, etc with access, but am tired of relying on my customers software, servers, etc.

I have some experience with WAMP, but I am far better at VBA. I was okay at PHP, and was getting a grasp on JavaScript a few years back. I am also trying to decide whether to go with WAMP or LAMP, if web is the best choice. Also, should I try set up one site for all users that after log-in goes to company specific pages, or individual sites for each company? Should I host or use a service?