Like Critical Mass, the World Naked Bike Ride (WNBR) is gaining global reach. The London ride pictured above in 2008 is where it all began six years ago, and is the biggest ride with more than 1,000 riders, but the WNBR continues to grow in both number of cities participating and number riders willing to bare all. This year, over 10,000 are expected in more than 70 cities.

Brighton Beach, considered one of the U.K.'s most eco-friendly cities, is also a popular spot for the World Naked Bike Ride. In fact, the naked bikers in Brighton not only will ride this weekend, they went on practice rides way back in March (when the weather was decidedly less summery).

In addition to an occasion for showing a lot of bare flesh, the World Naked Bike Ride lets riders write their anti-oil, pro-bike slogans directly on their bodies.

Conversely, slogans aside, the ride can be the occasion for some lovely body painting and body art - getting painted or painting yourself is now a standard pre-ride entertainment - and it is also a good way to hide the body bits that make the police nervous.

Of course, if you are riding Down Under or in a nice tropical climate, there may be nothing more required for a naked bike ride than shoes and possibly a bit of sunscreen (sombrero optional).

Riders come in all shapes, sizes, and definitely colors. Here is a line-up of some bikers from the Byron Bay.

However, lest you think the naked bike riders only get seen from the back, here's a full frontal from Croc Boy.

And then, of course, if you are willing to get painted and bare naked for your ride but you'd still like a bit of anonymity, there's always a sparkly purple wig to keep you a tad incognito.

It seems obligatory to end with an exultant "bike-over-the-head" photo, as every World Naked Bike Ride seems to include many shots like this. This is one of the prettier ones, showing WNBR riders at Brighton Beach.