I'm assuming you are wondering based on the idea that it absolutely had to be spent. Being the saver I am I don't like to spend money unless absolutely necessary. However, if someone told me: "You have to spend the $1000 in the next week"... I would invest $100 - $200 in link wheels for my existing websites. I would invest $100 in blog commenting I would invest $100 in content writing and article submission (so essentially about half of it in marketing my existing websites) The remainder ($500) would probably go into ideas and new projects or potentially a tool or two that would help me in the process of link building.
I will make that to $2,000 in 15 days with PPC. Just contact me if you are interested and we share 50/50 profits.
If you did not say "Im going to save it" then I would best most of you would have lost your $1000 on PPC, or some other crap advertising that you have no experience with, or some other fad that you think will get you to the top of the game. most people spend money on their site trying to reach the stars..., and all they do is crash right back to earth dreaming about it all over again.
I would build a niche blog that will cost close to nothing and then spend the $1000 on marketing that blog.
Thats an impossible question to answer without knowing your existing skill set, without a proper plan you might as well paint the town red for a weekend at least you would have enjoyed it! How about giving some more information about yourself and what you would like to achieve so you can get some more focused answers. John
Go on holiday. Failing that, personally I would purchase content. Content for my own sites, and content for linking.