Ideas for Powerbook modding?

Hello - so with the recent purchase of a mac pro, I have a 12" Powerbook which I'm realistically never going to use for any actual work again.

The DVD drive is totally shagged, some keys are missing and it's generally had a lot of use in the 4 years that I've had it for. So I'm thinking that I could use it as a hobby computer. Aside from building a PC about 10 years ago, I'm not very experienced in these matters, but I love sinking my teeth into projects.

So does anybody have any ideas as to what I could do with it? Say, ripping out the DVD drive and putting another HDD in... an unadventurous idea maybe, but that's why I'm asking you guys