The most conmmon maybe for a workstation I would say is this:
swap - 100 MB
/boot - 16 MB
/ - the rest of your hard disk usually.
Its good though to make a /home and maybe /tmp as well.
/home can be however big you want or depends on what you will be doing work wise. You can make your /tmp any size you want, but not necessary to go over 500 MB or 1 Gig, again depending on what type of work you will be doing. Its good though to have the /tmp, when your log files and stuff get overloaded for particular reasons, if its on its own partition, once it reaches the limit, it can't affect the rest of your partitions and directories taking up all your space.