I put together what I would describe as a blog hub. There are 18 different riders US and UK based and amateurs through 4* professionals. http://outsidethehorsebox.com. There is also a vet, groom and a sports physiologist who contribute. Not everyone is super frequent but having everyone together means there are generally an update or two a day.
I post several times/week on Equine Ink and once a month publish a Blog Carnival which is a collection of posts from other blogs. Any one can submit a post to the Blog Carnival -- it's a great way to get some new readers or find new blogs to read. I linked to the latest one above.
I'm not sure mine qualifies as a blog per se but I've had people refer to it as such.
I think of it more of a sporthorse and small farm resource site. I do describe why I like certain products or do things the way I do, so I guess it's kinda "bloggish" (apparently I also like to make up words in the process!)
I blog regularly as well; address is in my signature. Mostly a lot of rehab these last few months but I might have riding to talk about soon (!!!) and in the meantime I do a lot of volunteering, some book reviews, some movie reviews.
Mine only dubiously counts since I'm not planning to event this year -- it's about our side trip into distance riding (and readapting to a more go-it-alone lifestyle) -- but horse and I have run a couple of seasons at Training and we're continuing to school and volunteer (well, that's just me). The link is in my signature for those who might like that sort of thing!
I just started a horse related blog. It is a little daunting putting myself out there, which is why I don't post much on this BB anymore, but I do want an outlet to write down my horse musings and figured a blog would be an easy way to do it. I also feel like I've tormented my FB friends, many of whom are not horsey, with enough equine stories, and I need to find a more receptive audience ha ha!