Used Distro is Debian Squeeze with some package from Wheezy/Sid.
For plug electric guitar on pc need of some specific hardware for connect guitar (normal sound card are not goot for guitar electric signal), I use Behringer UCG102 device (linux compatible, and with apps for linux within!!! see behringer ucg102 on debian squeeze).
For use this device you need a realtime kernel, and you get it with three way:
Then set jack for realtime, with qjackctl and Behringer UCG102 I have this:
Last launch a apps for guitar effects like guitarix, rakarrack, jack-rack or creox and use your guitar with favorite effects.