Arbitrage - where to look for these companies?

Where to discover what companies are -

• planning on merging,
• attempting a hostile takeover 
• spinning off a business, 
• doing a liquidation, 
• planning a share buyback, or
• reorganising into a trust or partnership?

Keep a vigilant eye on the financial press and any and all services that track such corporate events.

• Wall Street Journal
• Major regional newspapers for investment opportunities
• Google:  search the words "tender offer" and "mergers"
• Internet paid services e.g., mergerstat.com
• Internet free services e.g., search engines at: 

Yahoo!  http://finance.yahoo.com/news/category-m-a and http://us.biz.yahoo.com/topic/m-a/. , MSN http://news.moneycentral.msn.com/category/topics.aspx.topic=TOPIC_MERGERS_ACQUISITIONS.