The infrastructure and offer for mountain biking and cycling in and around the Soca valley is much increased the last years.
One of those developments is the cycling portal bike alpeadria. This portal provides detailled information on many cross border cycle routes on different levels, so for groups and families (cycling) and real mountainbike trails. There you can also find trips, routes, tracks and downloads. Some of those routes are via Tolmin-Nova Gorica-Corno to Rosazzo-Cividale-Kobarid, others are the so called Adria bike route which starts at Kranjska Gora-Tolmin and Nova Gorica and goes to Koper and Ravenna.
There are also the Trans Slovenia 1 and 2, cycling routes via Kranjska Gora to Tolmin and Portorož. On adriabike you find also a set of digital maps with important information for key cycling links in the valley, connecting routes with neighboring regions and some local tours in various fields. These routes pass places like Kobarid, Drežnica, Breginjski kot and the Šentviška plateau and Baška Grapa. The maps on both portals are also usable on mobile devices.
A third known mountainbike information source is the book from Peter Immich, 'Slowenien - 30 Mountainbiketouren im Soca-Tal': Here you find links but also printed maps in full detail, with real mountain bike tracks.