Send text messages from AIM: Your PC can send texts to a mobile phone for free. Within an AIM client, send a text to the number with + and the country code prefix. For example, a San Francisco message might be directed to +14151112222.
eBay and Craigslist
Mind your eBay reserve: Tiptoe through starting prices when auctioning off an item to save money. If you're pricing something near eBay's thresholds of $1, $10, $25, $50, and $200, cut back by just a cent to save yourself a little cash, which can add up for high-volume sales.
If you list something at $199.99 for example, eBay charges $1. For a $200 starting price, eBay charges $2. For more information, check out the eBay Fees page.
Spell poorly: If you're buying hard-to-spell product, try searching for misspelling or common typos ("playstaion"), or enter * as a text wildcard such as "playst*". (eBay will find hits for one or more additional characters.)
You might stumble over auctions that others haven't found--which means less bidding competition. If selling, enter a few of those errors into your listing to snare misspelled searches (though probably not in the title--you don't want to disappear from the correctly-spelled search results).
Search Craigslist with RSS: Keeping an eye out for a free leather couch on Craigslist? Save yourself from searching every 10 minutes by setting up an RSS feed for the search results by entering your search within Craigslist and clicking the RSS button in the lower-right to add it to your RSS reader of choice.
Entertainment Extras: YouTube, Hulu, Flickr, iTunes, and Xbox Live
Download YouTube and Hulu: Watch online videos away from the Internet by downloading them to your PC. The simplest methods usually work best for noncommercial video, such as random YouTube home movies. But at press time, I got StreamTransport to save videos even from Hulu. Play clips back with VLC.
Watch high-quality YouTube: Bump up the resolution in supported clips. Just click the number and arrow in the play bar; it's likely 360p by default. Pick a higher number for the best quality.