NRDC's annual Testing the Waters report is out, detailing the numbers and causes for beach closures in 2007 (aqui en Espanol). Great Lakes, you're not looking so great.
I first encountered this report back in 1998, when I was looking at the data for the Heinz Center's national ecosystem report. When I started at NRDC, TTW was one of my earliest press duties; I'd get the summaries about 48 hours before they hit the streets and spend that time crunching numbers on Bay Area beaches. You can get as little or as much information as you want at the report site, by searching for your favorite beach or looking county by county at beach monitoring frequency, but the data resolution still leaves much to be desired.
That's because TTW suffers from the same problems as many long term environmental data sets. Beach monitoring and closure data isn't all collected in one central location, like at the EPA. Some of it requires calling counties and cities, each of which may have their own rules for what they monitor and how often. And those rules have certainly changed over the 18 years of TTW. While those policy changes can make long term trends difficult to tease out, a general trend is that the closer you look at water quality, the more fecal coliform you find. Water quality testing isn't necessarily expensive or difficult -- you can do it yourself as a Surfrider volunteer -- but it is one of those programs that tends to get cut when budgets are tight.
Keep that in mind the next time your municipality asks to upgrade its sewage system, because it's likely that those aging overflows and septic tanks are degrading your beach. Nothing ruins a "staycation" more than stomach flu.