There are a bunch of sites and forums devoted to rounding up the best freebies on the internet; Reddit's r/freebies (which is for physical items) and r/efreebies (non-physical) subreddits are both fantastic resources — check them out and be sure to submit things you find in your travels as well. Value Mags offers free magazine subscriptions, and Start Sampling has tons of product samples and coupons.
Some deals require Facebook likes or tweets in order to claim them, and nearly all ask you to submit personal information like your name and address (so use your judgement in terms of what you're comfortable giving out). And be aware that most of these offers are limited time and limited stock (although public domain audiobooks are forever <3). And as the age-old saying goes, when one internet deal you never knew you needed closes, another opens.
Right now, you could be the proud owner of...
1. A free Godiva truffle once a month.
2. Signed (fake) celebrity photos.
Celebrity Merchandise is a beautiful cesspool of quasi-random celebs and their corresponding swag; even shipping is free on some of these photos.
3. A TGIFriday's appetizer.
4. Kotex tampons and liners.
5. Head & Shoulders
6. Two free months of Spotify Premium, Hulu Plus, or Zinio.
7. Pet safety magnets/stickers from the ASPCA.
To alert rescue workers or neighbors that there are pets inside your house.