In my case I did a VERY basic photo shoot for a school prom (my first ever), and a retouch/merge job for another schools 2008 calendar recently. These 2 jobs alone have netted me advertising that would have cost around £1000.00, and paid work came from it within days.
You not only gain publicity/advertising for your business, but you are also giving something back to your local community, so in a way everybody wins. The calendar job also put me a good standing with one of the UK's largest school/graduation photography companies, and that has lead to other work.
So basically my message is, invest a little of your time in to the right local community projects, and you will be paid back for what you have done.

Janet