I disagree with DanGTD--There is definitely enough time to work on foreign language software, or writing your novel, or catching up on reading (pleasure or professional) or any of a dozen different things over lunch.
I use Rosetta Stone to study foreign language. It takes me 20-30 minutes to do a lesson, and because of the way they are structured, the principles stick. There is much research that suggests that working on something (writing, learning, whatever) for 15 minutes regularly leads to huge progress. That's because the little bits of work are additive. The important word there is REGULARLY.