My question is about how mantain windows over all, because i ussually put vlc or other windows like justin tv, etc, to work and do other things while i see that window…this is very useful in other OS´s because it help with multitask, at least for me.
Instead of adding a window wiget and cluttering up that area why not add it to the deskbar windowlist as currently right and left click have the same action left click could be used to add a per window control menu?
Currently there’s no convenient way to change any window’s behaviour. It’s regularly suggested to have an additional widget in the window tabs to set these kinds of flags. While I understand its allure, there’s the risk of complicating things. Putting “Always on top” there is bound to attract a “Fullscreen”, “No borders”, “On all workspaces”, “Send to next workspace”, “Send to previous workspace” etc. Hiding it with a modifier+right-click context menu instead of a widget may be a possibility. Still, I think it’s a slippery slope…
For now the kinds of apps you mention will have to implement an “Always on top” themselves. Haiku’s MediaPlayer and TV app do so.
If it’s really direly needed, you can hack it with this BeTip. 
Regards,
Humdinger