The DOD officially opened its 2009.2 SBIR solicitation yesterday. Proposals will continue to be accepted until 6:00 AM on June 17 (check out the solicitation for more details on this submission).
Meanwhile, the Air Force has already pre-released a draft of its 2009.3 SBIR topics. There are 224 Draft topicslisted in this pre-release. This gives you extra time to start fostering partnerships with contractors/primes, talk with the topic managers to find out more specifics, and write a clear proposal. It's NEVER too early to start!