You follow good practices, archive your priceless material in standard formats, and make it accessible through network services. Now where do you build applications to use those services?
HTML5 clearly understands the browser this way. (If you're not familiar with HTML5 yet, see http://www.html5rocks.com/) The blogosphere is full of comments about HTML5's audio and video capabilities, but its integration of local and networked resources raises more interesting architectural questions. HTML5 can give you access to local file storage or locally persistent databases as well as providing networked communication with remote processes. With an HTML 5 platform, the browser is more like a local application with good access to remote data.
If you've ever looked at developing browser-based web applications, or have ever thought about extending Firefox with its extension mechanism, you owe it to yourself to take a quick look at
http://code.google.com/chrome/extensions/index.html. That's all it takes to get started.