Ask HN: How to achieve and maintain mastery in spoken English?

I speak English as my third language and have always strived to improve my writing by reading a lot. We recently moved back to Europe from the Bay Area and I've noticed that my pronunciation and active vocabulary has deteriorated in a mere few months.

What resources are out there for native (or close to native) English speakers to improve their spoken language? I listen to podcasts but have found that the language quality isn't uniformly high.