Try sailinganarchy.com/ The forums include Crew Pool Anarchy. The description on the website says it all: "Come here to find a body. Or donate yours. Post your requests and a way to contact you. ..." Good luck!
email your club (if you are a member of one) or your local club and see if there is anything going. I am sure they will be happy to email out an ad to all the members on their mailing list, and that way someone might get back to you. My club does that and it has worked wonders.
The CYC maintains a register.
see here for info : http://www.cyca.com.au/editorial.asp?key=4788
here is an extract......
"If you are an experienced sailor who is interested in being placed on the Register of Interested Crew, please send an email, detailing your offshore sailing experiences, qualifications, preferred positions on the boat, contact information and crewing goals to [email protected]"
the other 2 main ocean racing clubs are Middle harbour yacht club (MHYC) & the Royal Sydney Yacht Squadron (RSYS) not sure what arrangements thay have.
good luck.