I've asked this before and gotten some good responses, but as the anniversary gets closer I'm hoping some new ideas and resources have come up.
Are there any radio news sources available to listen to? Preferably short 5-15 minute highlights. Or easily accessible newspaper headlines and articles?
you may want to keep an eye on this twitter account https://twitter.com/RealTimeWWI, which will officially start up on 28 June.
I have no comment on the providers of this twitter feed, and it doesn't appear to be from the same maker as https://twitter.com/RealTimeWWII, Alwyn Collinson. Here's the wiki article, and a news story on that one.
You've got a lot of options! The Twitter account already mentioned by/u/Searocksandtrees will be a good place to start, but you might also consider some of the following:
Do you have access to a college or university library? If so, you can easily get into the digital archives for dozens of different international newspapers dating back to the war, and consequently follow along day by day in a very literal sense. You'll also have the benefit of getting to experience it, in a sense, with all of the limitations and vagaries of available knowledge that the original readers did -- though of course with inescapable hindsight. The New York Times, the Times of London, the Ottawa Citizen, the Daily Mail and the Illustrated London News (if you can find it) are all ones I'd especially recommend.
The Spectator's complete archives, on the other hand, can be accessed without any university affiliation at all! Go find wherever you'd like to start and you can follow along, issue by issue, with all of the news, editorials and commentary they have to offer.
I can't think of any off-hand, but there will be a lot of people publishing online the diaries and letters of WWI veterans who matter to them in some fashion on the sort of delay you describe -- this could be an excellent way to follow along.
A number of websites already carry dedicated timelines of the war, often down to a day-by-day level. You could try this one or this one, for example.
Finally, in terms of books: Ian Westwell's World War I Day by Day is a bare-bones, no-nonsense sort of thing that I was happy to get for $4 off of a discount table. It's relatively light on detail, but it covers all the basics and exists in a handy coffee-table format. Less broad but far more deep is Saul David's recent 100 Days to Victory -- it provides an overview of the war through a series of 100 essays each focused on a particular calendar day. A lot of it is quit interesting indeed, and could serve as a source of welcome and accessible depth when taken together with everything else already listed.
I'm sure there are other means of dong this out there, but I hope these serve as at least a start.
On a slight tangent, I don't believe this is day by day, but the BBC is planning 4 years of programming to cover the 4 years of the war.
I actually JUST saw a calendar at Barnes & Noble for sale that serves this very purpose. Each day documents events occuring between 1914-1918 in World War I. Seems like an interesting lay-out.
I know this isn't a traditional AskHistorians answer, but I'm informing you of this calendars existence. Plus this time of year it will be at least 50%+ off.