flavours of shell - what is there?

[Tim Chown]

I realise this is a bit of an open question, but ...

I would be very grateful for any pointers or hints as to
where I can find out what different shells exist, and what 
their various pros and cons are.

The ones I know of are simply:
	sh	 csh	 bash	 ksh

Are there others?  Where are they principally available from?
(I've had difficulty locating ksh for SunOS Unix - is it restricted?)

Many thanks,
		Tim