Yes, this lesson probably would have been better suited sometime between 1997 and '99 when every kid in town was skankin' to the beat of the Supertones, Five Iron Frenzy or Buck.  However, I thought I'd write it now because there's allot a guitarist can learn from ska rhythm.  I would discourage you from reading this lesson and saying "hey!  I could go start a ska band just like the Supertones!"  because, frankly, before ska's downfall, everyone began to sound the same and I don't think that's a good pattern to start with any kind of music.  My suggestion is to learn from music and musicians, not to imitate them...  that's my spill.

Let's begin at the best place possible... the beginning!  Ska began in Jamaica and the guitar is very influenced by reggae.  What you need to learn first is how to play ska chords.  They are the complete opposite of power chords, because instead of relying on the low notes, ska chords are based on the higher ones.  Here are the basic chord shapes.  Their all different variations of the A ska chord.
 

Memorize those shapes and apply them all over the fretboard.

Ska rhythm can be a little more complicated.  One of the rythms' you'll hear the most is this.  On the down-stroke, you mute it with your left hand and press down the notes on the up-stroke.  You want an example?  Try this as I described it.  I'm sure you've been forced to listen to enough ska that you know how to did it... but do it slow at fist and build up your speed as you go.
 

(Click Here For An MP3 example)

Anyway, those 2 things are the basic back-bone of ska music.  Don't wear it out.  :0)