Starting points
[There is some work to do for me in working out how to do line breaks and paragraph separation in this CSS template. But I'm not doing it now, so sorry about the weird formatting...]
Now that we're actually up and running, I have a blog to maintain again. It's been a while since I could do that, but I thought I should probably start with a short account of this project's genesis and why, basically, I've set out to (convince others to) do it.
In an important sense, the point where this started was when the University of Leeds, in their wisdom, decided to take me on as Lecturer in Early Medieval History in mid-2015, because this project was one of the things I'd said I would do in my application. Leeds is a good place to do this because we have several people with frontier interests, among whom my Iberian-peninsula research focus made good sense. That's important, because obviously I couldn't have done it without the help of the Leeds Humanities Research Institute in shepherding the funding bid through their processes and the backing of my department in it, as well as the willingness of Alan Murray to take part. But obviously that's not the beginning of the story.
The frontage of the Queen's College, Oxford, with my differently-humble then-office just visible at top left. By Kaihsu Tai, CC BY-SA 3.0, Link
But you could go further back, and that would take you to 2009 and a blog post I then wrote fresh after reading a really-good chapter by Ronnie Elleblum, now Professor at the Hebrew University of Jerusalem.1 In it I found this extract:
One could live according to the customs of a province without coming under the jurisdiction of its prince. Every person knew what the border of his property was and what belonged to his neighbour. But such a property could have been divided between two or more rulers. The owner of the property knew to whom he was obliged to pay taxes and offer gifts on religious holidays, who would try him if he committed a heinous offence and who would try him if he committed a lesser offence. In the event of war, he usually knew where danger lay and on whose side he should be in order to fulfil his auxilium duties. But all these spheres did not necessarily overlap.
As I would later say to Emma, what theory of frontiers would this situation not break? This was what convinced me that medievalists should maybe generate some theory rather than trying to make ones from simpler or more legalistically-defined situations fit over our more complex ones. So that's an important moment of genesis, the point where the idea behind this project crystallised.

Cover of Frontiers in Question: Eurasian Borderlands, 700–1700, ed. by Daniel Power and Naomi Standen (Basingstoke: Palgrave, 1999)
1. Ronnie Ellenblum, "Were there borders and borderlines in the Middle Ages? The example of the Latin kingdom of Jerusalem" in Medieval Frontiers: Concepts and Practices, ed. by David Abulafia and Nora Berend (Aldershot: Ashgate, 2002), pp. 105-118.
2. Respectively Christys, "Crossing the Frontier of Ninth-Century Hispania", ibid., pp. 35-53, and Frontiers in Question: Eurasian Borderlands, 700–1700, ed. by Daniel Power and Naomi Standen (Basingstoke: Palgrave, 1999).
3. Eduardo Manzano Moreno, "The Creation of a Medieval Frontier: Islam and Christianity in the Iberian Peninsula, eighth to twelfth centuries", ibid., pp. 32-52; Daniel Power, "Introduction A: frontiers, terms, conceptions, and the historians of medieval and early modern Europe", ibid., pp. 1-13; Naomi Standen, "Introduction B: nine case studies of pre-modern frontiers", ibid., pp. 13-27.
4. Manzano, "Christian-Muslim Frontier in al-Andalus: idea and reality", in The Arab Influence in Mediaeval Europe, ed. by Dionisius Agius and Richard Hitchcock (Reading: Ithaca, 1994), pp. 83-96. I later tried to say something similar in Jonathan Jarrett, "Centurions, Alcalas and Christiani perversi: Organisation of Society in the pre-Catalan 'Terra de NingĂș'" in Early Medieval Spain: A Symposium, ed. by †Alan Deyermond and Martin Ryan, Papers of the Medieval Hispanic Research Seminar 63 (London: Queen Mary University of London 2010), pp. 97-127, and that originated in a conference in 2008, so there is another point that could be on this map...