For small business like a café across the street you might have to depend on the social contacts. However for a fairly large business the best way is the talk to you banker. Every business man would at some other point take a bank loan to support his/her business and would having issues fulfilling the loan payments . The banker too would be interested to covert his Non-performing Asset.
Layoff notices (WARN notices in Texas) are a great resource for companies who are needing to shed costs and are therefore probably feeling a pinch.
D & B rating ... published foreclosure notices ... business journals and business section of larger newspapers (NY Times, Boston Globe, etc.)
Aussie banks should be able to help you. Superannuation too gives out clues on stats.
Depending on your industry, business brokers are a great place to start. For example, in the hospitality industry you can often find distressed or closed businesses for sale on broker sites.
The listings often include liquor licenses, equipment, etc. Details on broker listing sites often, but not always, will list selling price, annual gross profits, cash flow, and other financials. You can also find reason for selling, type of business, number of employees, etc.
Here is one I have found very useful http://www.bizbuysell.com/