I found the following as written by Reinhard Scharnagl; additional information may provide some other ideas...
Welcome to Chess960 / Fischer Random Chess
On June 19th, 1996, in Buenos Aires, Argentina Bobby Fischer published a proposal for an extended game of chess. With rules for a more active game of chess he intended to prevent the complete theoretical exploration of the royal game. Especially his variant challenges the creativity of chessplayers for every new day.
Chess960 differs only negligibly from traditional chess: a) the initial setup of the bigger chessmen will be drawn complying with certain rules: the king always will be placed between the two rooks, there will be a bishop on the white as well as on the black squares, b) there are explicit rules for a more generalized defined castling.
By the basically provided possibility of castling and the corresponding positioning of the king between the both rooks the Chess960 beneficially differs from the also well known Shuffle-Chess.
By that Chess960 really extends the included present game of chess. That conventional version simply is one of 960 possible initial setups. So Chess960 is ideal to have chess-algorithms compete each other. There also are tournament experiences e.g. after 2002 and 2003 again at the Chess Classic Mainz 2004.
Chess960 provides a better comparing of chessprograms' quality, because fortunately still no confusing huge opening library exists for that.
Castling Rule
There is a very important property of Chess960, that on principle castling is possible (like in the traditional game of chess). Therefore is guaranteed, that the king initially will be positioned between both rooks. All castling preconditions from normal chess will be applied analogous.
Though the rules partially require to be stated more precisely, for to fit to all the possible 960 variants:
1) Castling is possible only between each still unmoved king and rook at their baseline.
2) After castling with the right rook the king will stand at the g-line and the castled rook at the f-line, after castling with the left rook the king will stand at the c-line and the castled rook at the d-line (it is possible within some variants, that only one of both figures will change its position).
3) Castling is permitted only, when nothing is standing from the king to his target square (incl.) except an involved rook, and when nothing is standing from the rook to its target square (incl.) except an involved king (from that it can be concluded, that all the squares must be free between both figures). [Here the FRC rules unfortunately are less precise compared to the one of Chess960: the question, whether third figures may be overjumped during a castling or not, really stays unanswered.]
4) None of the squares from the king to his target square (both included) may by threated by a check (particularly when a king is in check any castling is prohibited).
5) It is advisable to announce any castling for to avoid possible conflicts with existing moving rules (the move of castling must be started as a king's move, but it has not to be a valid simple king's move after the first let go of).
6) Alternatively it could be done like described as follows: the king will be moved first outside the playing surface next to his target square. The rook will be placed at its target square (if necessary). Finally the castling will be finished by setting the king on his target square.
Those rules of castling seem to be complicated. But practice shows fast, that they will be understood intuitivly.
Arena GUI and FRC
Though UCI and Winboard protocols still do not support Chess960 as need be, with the Arena GUI, a magnificent piece of software, there the possibility to play Chess960 against the FRC programs of the early engine pinoeers has been established. Thank to Martin Blume and his team for that!
For sure there are some things to improve: the setup of FRC positions with sometimes unusual castling rights, the entering of untipical castling moves, where the king is not moving at all or simply one step, that could become a more intuitive handling, which seem not to be easy tasks. It is highly recommended to read the online help to that points.
The FRC Book (ISBN: 3-8334-1322-0)
The book (German language, 116 pages) distributes Fischer's ingenious idea, to break through the frontiers of the traditional game of chess. No question concerning FRC will be left unanswered, no matter if targetting castlings or the initial drawing of starting positions. The reader will be guided from the publishing of the idea in 1996 to the founding of the WNCA (World New Chess Association) 2003 and the awarding of the first Chess960 World Champion titel to Peter Svidler in the same year.
As a real reference book, which not only covers rule questions but also includes the World Championship games of FRC (CC Mainz 2003) and the actual world rank table of all protagonists of the Fischer Random Chess, it leads the reader out of the openings' jungle into the future of the game of chess and the computerchess.
Here is an article i found on the internet about chess960. I did play a few times, and although it was fun for a change of pace, I will have to side with the tradionalist on this one. Thank you all for your input and comments. Hope to see you all on the Board!
Chess960 – Discover 960 possibilities
Chess 960 is a variant of orthodox chess. In classical chess the starting position of the game does never change.
The idea of this variant goes back to the former World Champion Bobby Fischer, therefore it is also called Fischer chess or Fischer Random Chess. But only the randomized initial chess position is depending on chance not the result of the game.
In Chess 960, just before the start of every game, the initial configuration of the chess pieces is determined randomly, that means that the king, the queen, the rook, the bishop and the knight are not necessarily placed on the same home squares as in classical chess. There are 960 distinguishable starting positions, if we take into account some constraints: the king is placed somewhere between the two rooks to allow castling. Now try to memorize opening moves for 960 different initial configurations. Quite impossible!
That is why the aspect of a well memorized theory about chess opening move sequences is less important, what counts is the chess game itself, just in a different way. But, of course, those who are good players in classical chess have all their chances in chess 960, too, because the knowledge about position analysis, tactics and occupation strategy of the chess board applies here as well, just for different positions.
Chess 960 is also interesting for orthodox chess lovers because the initial configuration 518 is the starting position of classical chess.
Mathematically, orthodox chess is only a (small) part of chess960.