You can use [ctrl]+[alt]+[fX], replacing the X with any number from 2 through 6. This will give you the standard command-line login. Once there, you can switch between them with just [alt]+[fX], 2 thorugh 6. To get back to the GUI login, use [alt]+[f7].
If you want the system to boot to the command-line rather than X, then you would need to edit your /etc/inittab file. Look for the section...
Code:
# Default runlevel. The runlevels used by RHS are:
# 0 - halt (Do NOT set initdefault to this)
# 1 - Single user mode
# 2 - Multiuser, without NFS (The same as 3, if you do not have networking)
# 3 - Full multiuser mode
# 4 - unused
# 5 - X11
# 6 - reboot (Do NOT set initdefault to this)
#
id:5:initdefault:
Change the "5" in the "id:" line to a "3", and it will boot to the command-line. You can then get to the GUI, after loggingin, with "startx".
