You might be thinking of the Stay, Drive, Ride promotion. That ended on April 30. It required 3 activities with hotels, car rental agencies, and/or limo services. The bonus was 50% and registration was required. However booking using a specific link was not required. Thread: 50% Partner Bonus Miles Promo to 4/30.

The only 5000 miles promo I can recall is the recently expired Budget/DL promo offering a 5K bonus on a car rental of 2 days or more. That one expired on May 31. It did not require using a specific link or registration - just a coupon code on a qualifying rental. Thread: EXTENDED: Budget 5000 miles/2 day rental till 5/31/2010.

There was also a promo to get an extra 1K for renting a car using DL's portal. That one ended April 30 IIRC.

AFAIK there is no current thread for consolidating Delta promos. Probably because there are not that many going on to warrant such a thread at this time. Last year there were so many mqm, cc, car, hotel, and DL promos that the DL forum did have a consolidated thread.

For the record, you can earn over 4500 US Div Miles through Avis and US right now:
3000 bonus miles for 3-day rental with Avis until 3/31/2011
Summer Blockbuster 50% bonus miles

You can get a 100% bonus on purchasing SkyMiles right now:
Buy Miles With DL AMEX get 100% Bonus .

Marriott has a SM promo this summer:
Delta SkyMiles® 60K Promotion: Earn Up to 60,000 Bonus Miles.