Always disclose your affiliate relationship. Most visitors will probably understand that graphic ad will lead to your getting paid, but if you write a review or use an in-text link as a recommendation, you want your readers to know that may lead to compensation as well. This ensures you retain transparency and trust with your readers, but also, it's required by the FTC's endorsement rules.
File-Sharing: Web sites that host directories of music, movies, games and other software. Users upload content to file-hosting sites and then post descriptions of the material and their download links on directory sites. Uploaders are paid by the file-hosting sites based on the number of times their files are downloaded. The file-hosting sites sell premium download access to the files to the general public. The websites that host the directory services sell advertising and do not host the files themselves.
These ways of making extra money cover a wide range in terms of compensation and prestige. Check out the options to see what could work for you, keeping tabs on a projected per-hour rate so you can see what would be worth your time. The list is loosely arranged by 1. jobs requiring more skill or expertise, 2. gigs needing less and 3. things you can sell. And if you think of any good options I missed, please let me know in the comments.