If it is 3D you’re talking about, export it to a scene of jpg’s.
Import the jpg’s into Flash, it automatically detects the other images and imports it to the timeline.
Create a swf (flash web format) but don’t make it any bigger then around 100k unless you’re creating a Flashbased website.
If you use PNG you can export it with transparency too, very convenient.
Embedded avi in a website is inappropriate, I don’t think some browsers allow it.
They all accept Flash though.
If it’s only 2D you need, you can use something like Swish.
It automatically exports to SWF and you can do some cool stuff with that.
There’s also something called SFlender. A Blender export to SWF.
It makes vectors of your 3D environment.
Don’t expect anything fancy. It has large filesizes if your anim is too big.
It usually has poor quality.