If possible I try to castle queenside for the reasons mentioned above.
1. Bring the a-rook further into plan
2. Its a different look for the opponant
3. The a-pawn is undefended, but its a small trade off (if it gets attacked, move it forward a single square).
Sure, it all depends on the game. I dont know if castling queenside is inferior, even if it is - i doubt my level of opponants are advanced enough to take advantage of any small advantage there might be.
In many cases you have to spend a tempo to bring your rook onto an open file when you castle kingside, so depending on the position the instant activation of your rook when you castle queenside could counterbalance the tempo that you may have to spend defending the a-pawn.
I really like to castle queenside at my beginner age.
but I'm on that diagonal when I castle queenside:
Yes, castling queenside is a very good option if you have a open or half-open d-file.
Anyway, it's covered by the biship :)
Queenside castle is an obvious alternate to Kingside. The advantage would rests on the situation at hand...sorry, just a general thought.
I cant get the pieces to castle? I'm not moving out of or through check. Whats going wrong? Only got 8 hours left to move! Help!
Are you moving the King two squares? The game will move the Rook for you if castling is legal.
ETA: This game? http://www.chess.com/echess/game?id=126500528 You can't, you've moved your King <--- not advice, clarification on a rule.
0-0-0 is where it's at, man.
It all depends on the specific position. I castled queenside against the Loewenthal Version of the Sicilian (B32), and it turned out to be a big mistake, especially since I had already made the mistake of playing 5. Nxc6 instead of 5. Nb5.
As White against any king's fianchetto-based defence I always liked castling Queenside to allow me to rush my pawns against the Black Kingside, but it's not a guarantee of success. 
I agree JamesColeman. That weak pawn can be a bummer but it all does depend on the position. Queenside castling can be great fun for a counter attack when your opponent has castled kingside; it can be a shock for an opponent who has made the mistake of taking tonnes of time to prepare a kingside attack only to find the king leaping out of danger, and bring a rook into play that the opponent isn't always expecting. People usually castle kingside because it is the safer option that doesn't lose a move to protect the weak pawn.