Mandarin

• ChinesePod - Learn Chinese with free lessons, vibrant community, web review, vocab study & more.

French
Spanish

• SpanishPod - Learn Spanish with free lessons, vibrant community, web review, vocab study & more.
• LoMásTv - Authentic Spanish videos include television programs, music videos, interviews, documentaries, and travel.

Cantonese

• Cantophilia - native content with transcripts
• Cantophilia - a few articles on the subject of learning chinese
• Chinese Character Database - from the University of Hong Kong, with sound files

Japanse

• A Japanese guide to Japanese grammar - explains Japanese grammar in a systematic step-by-step process
• Teach Yourself Japanese - rather old page, but very resourceful