DS2 (nearly 7) has just started piano and it's fantastic. It gives him an extra interest to explore and develop, and it's quite time-consuming too.
DS1 (8.5) is passionate and enthusiastic about everything at school, and is very academic. In his spare time he just develops his school interests - science, literature, humanities. Like any other 8 yr-old he loves the PC, gameboy, and TV, but has no other "outside" interests.
So what could he do to broaden his world a bit? He's not musical and not sporty (tried a few and nothing fits so far). We'd like something that will be time-consuming but quite cheap.