Best method of Error Correction in Quantum Key Distribution
Actually, there is a lot going on in the research of better and faster error correction codes for QKD. The biggest bottleneck of the CASCADE protocol is that it requires a lot of classical communication between Alice and Bob.

A lot of work has been done on LDPC codes. You can have a look to the following papers:

-Efficient reconciliation protocol for discrete-variable quantum key distribution (arXiv:0901.2140v1)

-Rate Compatible Protocol for Information Reconciliation: An application to QKD (arXiv:1006.2660v1).

Moreover, I suggest to look at the slides at https://sqt.ait.ac.at/software/projects/hipanq/wiki/Schedule where there are many talks about error correction in QKD.

Finally, regarding the applications, I would like to point out that the demostration that has been done in Tokyo was also implemented using LDPC codes (see arXiv:1103.3566v1 on page 13 for a reference).