Over the past year and a half I've spent a considerable amount of time encoding videos for flash. Since videos are usually huge, it's always a delicate balance between good quality and good user experience. As subjective as these "standards" may be, I thought I'd share how we in the biz encode our videos for online use.
flv encoding specs
VBR, 2 pass
Video target bitrate: 850 (something around 1000 is a good place to aim)
Audio bit rate: 128
Keyframe rate: usually 25 (more keyframes = better quality...but be careful)
You can find a more detailed explanation here: Encode to FLV
