Fun openings for castling long?

Depends on what level you're playing at or trying to play at.

A somewhat solid option with white is to just play the Torre Attack (d4, Nf3, Bg5, e3, c3, Bd3, Nbd2, Qe2/c2 - sorry, it's a d4 opening), wait for your opponent to castle, and then castle on the opposite side. Of course at some level (maybe 1700?) this becomes pretty risky, as black will usually have pretty quick play on the queen side.

You can also just play 1. e4 and play mainlines, many of which will involve white castling queen side and attacking on the king side. Lines that come to mind are: most of the Sicilians, the Caro ...Bf5 mainline (if black chooses to go ...0-0), the French Steinitz (sometimes), the Petroff with 5. Nc3, the d3 anti-Berlin (see Wei Yi - Navara from Tata Steel). But of course there are always going to be lines where opposite side castling is not really possible: the French Winawer, the mainline Ruy Lopez defenses, Sicilian sidelines, etc.

With black you can just play some kind of mainline Sicilian like a Najdorf or Dragon. Usually if white wants to prove any kind of advantage they will castle queenside. And against d4 the King's Indian probably gives the kind of play you want, even when the kings are on the same wing.

/r/chess Thread