How can I maximize my time waiting for my computer to start up?

Or as we called it in the old days, boot. There are basically three wait times getting my computer up and running. First there is the wait time from pushing power to the login screen. Second, the wait from login screen to having the full screen drawn with program icons, task bar, etc. ready to be clicked, third is the time it takes for the programs I want to work with to launch.

Does Windows XP (or 7 for future reference) continue loading in the background before I login? If I turn on my computer at work and then go to get coffee, will I only save the time from power up to login screen, or will I also save some time from login screen to icons ready to click? Should I get coffee after pushing the power button, or after logging on? (assuming I’m not worried about security or getting logged off automatically)