I would strongly suggest you either ideally do as others have suggested and put in ducting that means you can pull more cables later, or, if for some reason you can't, put in both fibre and cat5e - even if you only initially use the cat5, you've still got the fibre there for later, as running new cables without ducting will cost a fortune (in the redecorating costs if nothing else!)

The tricky bit about the whole thing is software, while there are lots of good individual bits and pieces for the various functions you probably want (MythTV for example), there isn't anything (AFAIK anyway) that lets you manage all these things centrally - if you want the house to be really clever, then having everything coordinated by one system is what you want...