| Derklord |
Have you tried searching for feats for containign the term "longsword"? Or for "sword"? Not all of these are their own fighting style, but Sisterhood Style might fit the bill. There's also a Swordplay Style chain.
| Mark Hoover 330 |
Sisterhood Style seems to focus on wielding a longsword and light or heavy shield exclusively. The Inspiring Sword Divine Fighting Technique also focuses on using a longsword. Elven Battle Training is a an entry to the Elven Battle Style chain of style feats. That's all I could find specific to Longswords on the SRD, but there might be more out there.