setterm -blank nn will tell the console driver to blank the screen after nn minutes of inactivity. (With nn = 0, screensaving is turned off. In some old kernels this first took effect after the next keyboard interrupt.)
The s option of xset(1) will set the X screensaving parameters: xset s off turns off the screensaver, xset s 10 blanks the screen after 10 minutes.
The video hardware powersaving modes can be enabled/disabled using the setvesablank program given in the starting comment of /usr/src/linux/drivers/char/vesa_blank.c.