Hilton and Marriott are giving instant, free Silver status on both programmes.
The Hilton sign up offer is here, and you can simply log in and put your details in the boxes:
The good part is that you only need to stay 4 times within 90 days and it will be upgraded to HHonors Gold status. The offer is targetted to Accenture employees, but in reality anyone can sign up. Hilton Silver won't get you that much, so this promotion's pretty good to at least get you to Gold very quickly.
On the other hand, as reported by Canadian Kilometers, Marriott requires you to sign up for a brand new account here, and does take up to 48 hours to complete. But at least it'll save you the 10 nights requirement to hit it ‘the hard way'. Once again, it's a targetted offer, but anyone's able to sign up.