>mount <devicename> <mountpoint> should do it.
>eg: mount /dev/hda1 /mnt/c

Note in some cases (like me with knoppix 3.2) you have to supply type too
ie. the same example (if in fat) will look like
mount -t vfat /dev/hda1 /mnt/c

For more info for valid types
Use
'man -k' on your distribution