I don't have much free time to spend on programming but when I do it's usually fixing or improving existing software. I'm at a point now where I can see the end of my current list of projects (Vampire Castle DS still to go) and have been thinking about some other new cool software to write.
Here's a few ideas:
A virtual butler with a British accent. Ever wanted your own butler to notify you, tell you the time, start programs, do web searches or generally be a dumbed down Tony Stark Jarvis prototype? Voice recognition is obviously going to be a key factor.
Local on the 8s (Nintendo DS):
A Nintendo DS weather program that simulates the Weather Channel with some truly unique features that cannot be found in similar DS software (I'm keeping quiet about features in this one).
A drag and drop media converter to convert your flacs/oggs etc suitable for your media player and pull in meta data (such as photos, videos, text) from the web during conversion, which will be copied to your player. Originally I intended this to convert my oggs to low (128kbps) bitrate mp3s so I could fit them on a low memory player, but obviously this program can be so much more.