Tartuffe:  This is one really low down snake.  (No offense to snakes)  He pretends to be a holy man, but he is far from it.  He goes around acting charitable and repentant, and fools some into thinking he is a very holy man, indeed.  The main people he fools are Orgon and Madame Pernelle.  He uses his false position as a holy man to gain access to Orgon's home, and later Orgon's property and secret papers.  My personal opinion of him is that I can't stand his character, and was ready to punch his lights out by the end of the play.

Orgon:  He has more money than he has sense.  One of his kind are born every minute.  Apparently, this trait is inherited, too, because his mom is the same way.  He is completely taken in by Tartuffe.  He loves Tartuffe more than any of his family, believes what he says, and is blind to the truth of what Tartuffe really is.  He also has a very nasty temper, which leads him to do some really stupid things throughout the play.

Cleante:  This guy is calm, cool, and level headed.  He is the voice of reason and rationalization throughout the play.  He tries to reason with Orgon, and later Tartuffe.  His arguments are logical and down to earth.  Unfortunately, all that doesn't do much good until Orgon finds out the truth about Tartuffe, and at the end of the play, after Tartuffe has been arrested.  And even at those two points, all he is doing is calming Orgon down.  (Remember Orgon's temper?)  It's kind of a waste of talent, if you ask me.

Elmire:  This lady also has a good bit of reasoning power.  She is the one that succeeds in making Orgon see the truth about Tartuffe.  Before that, she was almost successful in just getting Tartuffe persuade Orgon into not making Mariane marry him.  It seems odd, though, that someone as calm and rational as her would marry a "ballistic maniac" like Orgon.

Mariane and Valere:  These two kids are strange, which is due, in part, because of when this play was written.  For instance, when Orgon tells Mariane that she is to marry Tartuffe, she does not say she will, but doesn't even begin to tell her father that she doesn't want to.  That has to do with the power of the father/husband over the family.  However, she really doesn't want to marry Tartuffe, but seems incapable of even admitting that out loud to Dorine.  And when Valere asks her what she is going to do, they have a big scene, which shall be elaborated on in another section.  Anyway, I guess what I'm hinting at is that, while she is really nice, Mariane is rather weak willed, wishy washy, and also stubborn.  Valere is stubborn, too.  However, he has a nice character trait which shows up towards the end; he tries to help Orgon flee from being arrested, even though Orgon canceled the engagement between Valere and Mariane.

Dorine:  Even though she is a mere maid, she has a great deal of common sense.  "Common people" [i.e., not the really rich ones] having common sense was a big thing back then.  Wish it was that way today.  ;-)  Anyway, she is the reason that Mariane and Valere don't break up half way through the play.  While she may not be as calm as Elmire or Cleante, she is by no means any less clever.  She also has an attitude, which makes the story very interesting in certain scenes.

Damis:  He is not exactly a very deep character, in my opinion.  It is clear, however, that he is his father's son.  He is just as quick tempered as Orgon, which causes a good deal of trouble.  He does not think things through, nor does he try to plan ahead.  I guess it is true that you grow up to be your parents.