Need Ideas for Web Development Projects

My areas include: Java, C/C++, Python. I want to do my major project and need ideas for web development projects. I have thought of providing live demo online of applications like linux applications before users can download those apps. Is this a good project and if it is, how can I proceed; what language and tools to use?

Also, is there any project related to Linux that I can develop? I need some ideas in this aspect.