The new Hotmail introduced a handy feature when it comes to managing newsletter subscriptions; since the CAN-SPAM Act was passed into law, all email marketing mailing lists must include an unsubscribe link somewhere in the email, typically in the footer. But, while complying with the law, the process is not always made easy: thankfully, Hotmail now includes a "universal un-subscription" mechanism of sort, which lets you get rid of invasive newsletters with a single click. This tutorial explains how to unsubscribe from a newsletter using this Hotmail feature (available when you check Hotmail from a web browser).
Note that some email marketing newsletters / mailing lists may not be recognized by Hotmail, in which case you would need to manually unsubscribe from those mailing lists.
Follow these steps to unsubscribe from a newsletter:

If Hotmail displays the Unsubscribe link, it means that it has recognized that this newsletter is handled by one of the most common mailing list management software, with whose un-subscription mechanism the Windows Live team is familiar.
If automatically unsubscribing through Hotmail, and manually removing your subscription did not work, the next step is to mark the email as spam: some companies make it intentionally difficult to unsubscribe, if not outright impossible. In this cases, reporting these newsletters as junk mail will automatically go to the Junk mail folder, no longer clutter your Hotmail inbox.
After a company notices that its emails are filtered as junk mail increases the chance that they'll correct their behavior and allow for an easy opt-in and opt-out subscription system.