Over at the Blog Herald there is an entry about how to come up with ideas for content. Here’s my two cents:

Don’t forget one of the most basic sources of information: the world around you! Pay attention to billboards - they are often one of the first signs of upcoming events and attractions. Listen to snippets of conversation in restaurants and coffee shops - people are always talking about something that is blog-worthy, to some extent. Flip through the local ‘zines in your community - see what sort of community events are happening. Sit in at a local school board or city council meeting - chock full of ideas for civic-minded blog entries. Keep your cell phone handy, too — snap a picture of something that you will want to blog about later, or text yourself a brief message about something you hear and might want to blog about later.

In short - just pay attention to everything around you!