Normal photography work like headshots and PR work are a reasonably sensitive area for blog posting. I've been doing a number of shoots for a performance group with under 18 recently, so as you can imagine, even posting an out take is a bad idea. Headshots can be a different matter and while some people love it, others prefer not to have stuff posted. For this kind of work, I don't even ask anymore and simply don't post. Of course, it makes for boring blogs.If you are posting photos online, you really do need the subject's permission, even on your blog. Ultimately for most photographers, the blog is part of their marketing material and therefore commercial in nature. While we may assume that verbal permission is okay, it's much better to get it in writing. This written permission is the Model Release.A good model release should contain the date of the shoot, the type of photos/video taken (we are in the Video DSLR age now!), both a printed name and a signature. With regard to the wording, normally it declares that the model waives all rights to the photographs, is aware of the photographers legal copyright. I also include text indicating the shoot was carried out in a professional manner and the signature is not given under coercion. Finally, some kind of payment is expected to bind the contract. For example, with TG4, the Irish language TV channel, a token €1 is offered to all show participants (whether or not it gets paid is another matter!).iStockPhoto have a nice section on Model Releases and a sample model release at http://www.istockphoto.com/faq.php?FormName=FaqSearchForm&Category=13.