As Stephen nicely posted earlier, RSS feeds are a very powerful way to keep up with the literature -- they "push" the information to you. In addition to subscribing to individual journals, you can subscribe to a PubMed search! This will let you keep up with ALL PubMed indexed journals.
To subscribe to a PubMed search, first go to www.pubmed.org and enter your search terms. Once you retrieve a search listing, you'll see a bar that says
Display Summary Show 20 Sort By Send to
The SEND TO drop down box will allow you to select an RSS Feed. Once you select this, you'll be taken to a page with a button that says "Create Feed". When you click this, you'll get a new page with a little orange XML button. Click it and your browser will give you the option to subscribe to the feed. Once you subscribe, there are lots of ways to read RSS Feeds, which we'll probably get to in another post.