I want to create an "up to date" installation disk from my own one. So after installing the system shouldn't need to download any update. Is that possible? If so, how? Thanks.

its called time cap...

I don't believe it is. TimeCapsule restore would be limited to the same platform it was backed up from?

I think what the OP is after is the idea of slipstreamed DVD including Snow Leopard *&* the latest combo updates. In the Windows world this is referred to as a slipstreamed install.

For example you could have the latest build of SL plus the latest combo update slipstreamed in and this should work flexibly across a number of platforms.

Unfortunately though I don't know if it's possible with OSX. It's a real time-saver in the Windows world though if you have a number of machines to deploy or if you're constantly building/assembling VMs for example.

I do not think this is easy at all; I remember I once asked Apple engineering to prepare a one-piece update for a generation of Mac OS when that generation is replaced by a new one (e.g. a global upate bundle for 10.5.x).

The simplest way is to download the combo update of the given system (e.g. 10.6.7), which usually includes other updates as well (e.g. security updates), restart, then see what software Update still detects. Downloading the latest updtes, and keeping them on the disk is the fastest way to update, even if you have a fst internet connection.

Otherwise, of course, if you are an expert, and can put together stuff so as to have the latest software. I am afraid I cannot offer any further suggestion here.