for a single user system, i usually do
/boot 100 megs
/ 10-20 gigs
/home the rest of the drive (100 gigs in my case)
swap: a gig
This allows you to reinstall the system without loosing your home directories.
most partitioning schemes that seperate other areas (/var, /temp, ect) do so for security reasons. The basic thinking behind this is: a malicous user could fill your / partition by doing things that fill up /var, /log /temp, ect. This could bring your system to a halt because it woudnt have anywhere to write things to. if these filesystems are on their own partitions, it woudnt wreak nearly as much havoc on your system. as you can imagine, on a single user system, this would be much less of a concern.
the idea of a seperate /boot partition is simply to make damage control easier if you ever manage to pick up a rootkit. also, you may afford yourself some extra protection by mounting file systems that very rarley change (such as /boot, /usr/sbin, ect) read only, so even root cant change them without unmounting them and remounting them rw. Again, this is Probally way overboard for your normal desktop user.
btw, dont be fooled, i dont know wtf im talking about, im just repeating things ive read over the years that seem to make sence
Another VERY usefull note: linux can read ntfs with the correct drivers, and xp can read ext3 with the correct drivers. google it if your interested