What is management information systems?

Content Management Systems (CMS): What's a simple, lightweight but secure way to catalog all of my client information?

• I run a freelance design and web development firm. We have an increasing number of customers, and keeping their information (basic contact info, FTP information, various web and other account usernames and passwords, miscellaneous notes) in Excel spreadsheets is beginning to get tedious. I'd love a web-based solution so it can be accessed on the fly from computers that aren't mine (so, no standalone software), but it obviously needs to be secure if we're going to be storing passwords. I was thinking I'd make a custom solution with Drupal, but before reinventing the wheel would love to know about better solutions!

• Answer:

  If you don't mind paying, Basecamp could do the trick; it also would let you create projects for you to communicate to the client directly and more easily transmit documents and files that can't be attached to emails.