I would think that most all hosts support real streaming via HTTP.
There are 2 ways of streaming:
1) RTSP/PNM - requires a special Real server.
2) HTTP streaming - streams content directly from the web site's server.
HTTP should be fine for short clips, but for long clips that are 5 + minutes long I would suggest streaming them from a Real Networks server. Streaming from a Real Network server provides better seek speed, and is more robust then HTTP.