IBM has an excellent presence online, not just ibm.com but also the social space.
Although there’s no official IBM twitter/facebook/blog, there are thousands of IBMers on twitter, facebook, linkedin and other social sites – and hundreds of bloggers as well.
Just in case you’re looking for some IBM bloggers, you can find them (including yours truly) over at ibm.com/blogs. There’s also IBM Social Computing Guidelines, that define how IBMers should present themsleves online – worth the read.