Although Android is supposed to support HTML5, including the video tag, unfortunately this doesn't mean the Android supports open codecs such as Ogg Theora/Vorbis. This is a huge disappointment because Google has made a commitment to open, non-patent encumbered video. At this point the only option is to wait for .webm and hope that everyone support, implements, and uses it; or you can encode your videos as .H264 .mp4 videos, but that would be supporting patent-encumbered formats.