[avr-gcc-list] understanding timers

[Timothy Smith]

hello avr people i've been reading and working through various tutorials 
on avr's, and i've managed to to program one and make led's on various 
ports turn on and off, however i'm having a little trouble understanding 
the timer functions.

http://www.nongnu.org/avr-libc/user-manual/group__demo__project.html

that example is fine, i understand what's happening ( i think ) but how 
would i controll the speed of the led blinking? would i use a different 
ISR, such a timer compare?