Twitter's hashtags are a valuable tool to increase your reach and get more traffic when you tweet your links to your content.
My quick way to identify the hashtag I should be using for a topic is to enter the one word I feel describes my topic best as a search term in twitter's search. I then scan the first page of results looking for the words set apart from the rest of the tweet as hashtags. They look like this: #mmo #contest
Sometimes they're abbreviations we might not intuitively use, so those few seconds it takes to search are worth doing rather than taking an intuitive guess.
Not only does using a hashtag help you be seen within twitter, it can move your tweet beyond twitter onto gadgets on websites that are set to display the most recent buzz about a topic. The value in this for links to quality content (well described) is that it can help get your link in front of the very people looking for it, getting even more traffic.