I always create these partitions, and as of the last year, always on LVM:
/ - a few Gig
/usr - 24 Gig and mostly empty
/var - 4 Gig works for me, YMMV
/home - depends on how many users you will have
One of the most important is
/var -- if this is a separate partition, then when it fills up, you will not crash your root partition. Although I have never done this, some make a separate
/usr so that they can mount it read-only.
and I sometimes create these partitions:
/boot - even 1 Gig is way more than enough
The reasoning is that it's not always possible to boot from a RAID or LVM partition. Thus,
/boot can be a simple ext3 partition, allowing
/ to be more advanced.
If I will have a large number of large files, I will sometimes create a specific partition for these large files so the filesystem can be tweaked to be efficient at storing large files. Some people, if they will be serving NFS from a server, will create a separate partition for their NFS shares or even a separate partition for each NFS share. This depends on your needs.
Why LVM? As I've mentioned in answers elsewhere but forgot to mention here, it makes it a LOT easier to change your mind later and expand a partition. This has saved my butt already.
These are general guidelines. Of course, I expect that if your server has special needs, you'll take that into account and make partition reflecting these needs.