The Worldwide Pinhole Photography Day is April 28 this year. If you have never shot with a pinhole camera then this is a great chance to try it.
The easiest way to get started is probably to get a pinhole body cap for your favourite camera. I got one for my Pentacon Six from Randy Smith over at Holgamods. He can probably hook you up with a body cap for almost any camera out there.
But you can of course also go the DIY route and either build a camera yourself or modify an existing camera, like I did with a Kodak Brownie 127 (more on that some other time). I used the instructions by Mauricio Sapata over at on the Filmwasters forum for a very similar camera.
And finally you can obviously also buy ready made pinhole cameras. For example Gezim Fisheku does very nice large format pinhole cameras that he sells through eBay (I got the 8x10 one). And again there's Randy Smith of Holgamods who does the beautiful Da Vinci 4x5 (and also 8x10) pinhole cameras. And of course Holga makes the Holga WPC, a standard medium format film pinhole camera and a 35mm film pinhole camera.
Once you've decided on a camera you should read up on reciprocity failure (also know as the Schwarzschild effect) to make sure you correctly expose your film. If you have an iPhone I suggest you get the Pinhole Assist app which can greatly simplify your life in that respect.
So, get going now. WPPD is just around the corner!