Can anyone tell me if there is an easy way to identify companies that are raising capital...
Look for companies that have a sharp drop in share price :)
...as buying in the market as a share offer closes appears to be a good way of making money.
No, no, no! How well the company performs after the share offer will depend on how good the take-up is and that will depend on the company's future. The only way to determine how rosy the company's future is to make sure you do the research... as always! In general, avoid companies that request funding for day-to-day working capital rather than exceptional expenses.