(Request) A Browser Plugin for Managing Downloads

A problem with downloading files that I have is that the downloads folder ends up really messy. Lots of files that usually have no real correlation to each other. I like to keep things organized and have them in the places where necessary, but I want my browser to automatically know where I want certain files

I'll try and make this clearer: I want my browser to automatically download files with .mp3, .wma. etc extensions to the folder of my choice (e.g. "My Music") but I want files with .jpg extensions to go to different folders ("My Pictures") and so on.

Is there a plugin or app, or basically anything that I can use to solve this problem?