I started homeschooling my kids when they were halfway through 2nd and 5th grade. So I dove right in with the foreign languages. We do Italian and American Sign Language (I know ASL isn't technically a foreign language, but I think it's a beneficial skill for them to learn, so I categorize it under foreign language.)
We use lifeprint.com for our sign language and DuoLingo for the Italian. I just learned about a site called memrise that supposedly is really great for helping you to learn a foreign language, but I haven't yet tested it out myself.