Well, it all depends on what you are trying to achieve. We cannot guess that in your place.
The first thing that comes to my mind (it is almost diner time here) is cooking. Make a recipe database.
Make it produce grocery lists depending on the number of guests. Add search facilities depending on country, cooking time, ingredient, calories etc. Add foto, video possiblity. Tough enough, I guess.
What are your hobbys? Gardening, sport, film etc.?