A very large majority of the work published by historians appears in one of these three formats – journal articles, chapters in books, books. These formats allow for the evidence intensive and subject-extensive treatment that history favours. But there are lots of other ways to publish, especially online, and these alternative formats tend to cater to other needs than the simple presentation of research. Some early-career scholars find that their first published words take the form of book reviews. Journals receive lots of miscellaneous books for review and are often delighted to find someone – anyone – who knows enough about the subject to review them. There is a case to be made for only reviewing books after you’ve written one yourself – an experience that imposes a proper degree of modesty. (It also shows that, minimally, you know what you’re talking about.) If you don’t have a track record, be extra careful not to raise unrealistic expectations or to be too territorial. Normally you should be given the chance to proofread the book review. And of course you get ‘payment’ in the form of the book. Forums and roundtables are increasingly popular formats in journals and on blogs. They are excellent formats for stimulating discussion (of controversial issues or influential books) and for broadening the range of voices. They’re normally by invitation only. But you can be the host, if you can find a journal editor willing to entrust you with the task of putting together a forum. Often roundtables in print originate as live roundtables at conferences. They are chattier, usually shorter than full-size journal articles (say 3-4 contributions of 1-4,000 words each?), and don’t require the full scholarly apparatus, as they tend to be more argumentative and less loaded with evidence.
Some traditional publications (like book reviews) now often appear in online-only formats. There is no reason why you cannot include them in your C.V., just as you might print book reviews. But be conservative. If there is really no difference between the online version and its print equivalent – if you were commissioned by a reputable book review site, and you submitted a full-length review with a stable URL – then surely it’s the functional equivalent of the print version. But if it’s just a blog post, or some other more casual form of contribution, without apparatus, un-peer reviewed, it really has no place on your list of publications; it will just look like padding. A c.v. is an accounting of your scholarly qualifications, not an advertisement.