My Youtube video has been up for 3 years and it is obviously very popular. I already have google adsense and make a good amount from it. What else can I do to profit from it? I have over 75 million views all together. Any ideas?
in my opinion you can sell the ad place to any ad seller.
what about your video?
sell your video:)
or sell your site if you want the fast way out
Post a link to your site on the video. Most likely there is a way. Or maybe just tell the people on the description that you have more videos like this at your site.
You could put a textlink ad in the description. VDownloader (VDownloader » Download and convert YouTube videos for free) for instance pays quite well for those.
This aspect of youtube has always amazed me. Why on earth would anyone put up their material and let youtube profit from it? Anyone care to explain the logic?
To answer the question, there are a few companies that will place ads at the end of your video and let you profit share e.g. revver. Not sure how profitable a 3 year old video, already on youtube would be though.
what is the video about? I am wondering 
Its depend on your video if it related on music you can search mp3 affliate network
Visibility for one but Youtube has many partnership programs with successful channels ranging from small rev splits up to dedicated sales. All depends on what you’re bringing to the table.
It also depends on the “niche” of the video. But however, as the other users replied, you could advertise your own website/products in the description, or by editing the video.
250,000 views/day is quite a big number, you should definitely get some good money 4 that
Good luck 
Try to put links in the description ( to your site, affiliate links, etc ).
Can you show me your video also?