StreamInCloud is a free FLV (Flash Video) encoder. You simply create an S3 bucket and give StreamInCloud permission to read and write it. It then monitors the bucket for new videos, encodes them into the FLV format, and places the encoded version in the bucket. Of course, if the bucket is part of a CloudFront distribution, the encoded content is then available worldwide at high speed with low latency.
StreamInCloud encodes the videos at 512kbps and leaves the size as-is. This service is free; an advanced version with additional features and options will be available later at an additional charge.