Someone is going to suggest better thread titles, so I'll refrain....
It depends on whether the disk is IDE/PATA or SATA. The latter allows fewer partitions.
But then, you could always use a Virtual Machine. The ultimate limit is how much space is used for each distro.
The links below have some tips, but the resident expert here is Saikee. In his sig, there are a bunch of links to tutorials on multibooting. To find a member's posts, go to Search---select "advanced search" and then "search by user name"