Sign up via this link before you go there:
(Dead link: https://secure.venetian.com/APPS/VPC/vpc_becoming.cfm)
Take a printout of the confirmation and take it to the sign up booth. They will load your card with $15 free slotplay.
Also, if you get American Casino Guide 2010, there should be a coupon for $25 for Grazie sign up free play bonus. They should be stackable, hence giving you $40. ACG book costs around $13 at Amazon, but there are many other match bets and free plays so it'll pay for itself.
If you don't like risk, play the $40 through one of those crappy blackjack slots and it should return around $37-$38.
Good luck.