Match schedule for german 3rd league has been published:
http://soccerway.com/national/germany/3 ... ar-season/
Opening game will be Bielefeld - Aachen, two clubs who have recently played in the 2nd (and also 1st) league. Though Arminia Bielefeld is not the club which is famous for their ultras (and Aachen has been better at the old Tivoli stadium when their groups haven't been divided), the fixture promises a relatively high quality of support if you keep in mind that it is only the 3rd league.
During the season there will be a lot of attractive 3rd league matches this year, as Karlsruhe, Aachen, Halle and Rostock joined the league (in Rostock the club management decided to not re-open the stand of their main group Suptras, so up to 3.000 fans and ultras now don't have a "home" in their stadium anymore). In my opinion, Halle - Rostock will be the most interesting game, as Halle has got a really good relationship to Lok Leipzig. Halle's Saalefront attacked some normal Rostock fans several weeks ago while they were taking a group photo in Halle to support their club, which had big financial problems (in many cities Rostock fans were taking photos with messages like "City XY says yes to FC Hansa Rostock"). But keep attention on news articles days before the match. German authorities are likely to limit the number of away supporters or to regulate the selling procedure.
Other good matches: Münster - Osnabrück, Münster - Bielefeld, Osnabrück - Bielefeld, Chemnitz - Halle, Chemnitz - Rostock, Karlsruhe - Saarbrücken, Offenbach - Darmstadt, Erfurt - Chemnitz, eventually Stuttgarter Kickers - Karlsruhe and Darmstadt - Karlsruhe.