Opening systems for White which enable queenside castling In general, as White, I prefer to castle queenside and then start attacking with a kingside pawn storm. Every time, I hope that my opponent lets me do it.
For instance, when I play 1. d4 (or 1. c4), I hope my opponent does the King's Indian so that I can go to my Saemisch setup with queenside castling. Similarly, when I play 1 e4, I hope my opponent plays the Sicilian so that I can go for the Yugoslav or English attack.
However, in both instances, Black has to cooperate to let me castle queenside. For instance, with the Slav against 1 d4 or 1...e5 against 1 e4, it becomes difficult for me.
Hence, in general, is there an opening system for White where I can go queenside castling irrespectivly for how Black plays? The closest that comes to this seems to be the London system, but I haven't deployed it much in my games. I am mainly a 1. c4 player (and play 1. e4 occasionally when I know that my opponent might play the Sicilian).
The London System is unlikely to be your answer, as white almost always castles kingside.  If you want to castle queenside, then 1.c4 is really the last way you should be playing, as white rarely castles queenside in openings where the c-pawn is moved early.

On the whole, I'd say 1.e4 is probably your best bet, as the Sicilian is the most common reply, when queenside castling is possible in most variations with Be3/Qd2/f3 setups.  It is also usually possible against the caro-kann and scandinavian in the main lines (although black often castles queenside too), and also the pirc/modern.  Against the french you can play the classical with 4.e5, which often features opposite side castling, or the Reti Gambit.

Against 1.e4 e5, I think it's better to play main lines, but you can pretty much get a sharp queenside castling position by force in the Centre Game, where the main line is something like 1.e4 e5 2.d4 exd4 3.Qxd4 Nc6 4.Qe3 Nf6 5.Nc3 Bb4 6.Bd2 0-0 7.0-0-0. Objectively, black is fine, but most opponents will not be prepared for it and you may catch out a few people who think the Centre Game is bad and do not play seriously against it.

Not sure about rarer lines like the Alekhine defence, 1...b6, 1...Nc6, and such, but in my experience you don't face that stuff very often.

Of course, I cannot really recommend such a single-minded approach.  It's better for your game if you play all types of positions, and you can often attack with same-side castling.