The $8000 Federal tax credit for first time
buyer is availabe if you
close on a purchase by December 1st.  That means you would have to find the
house you want by around October 1st to make sure you can close in time, since it takes about 45 days to close, plus any extensions for last minute issues that come up. 
So if you need to find a house by early October,you should start looking no later than September 1st, to make sure you have time to find what you need.  That's just one month away now.  
Make sure you don't miss out on the free government money!