Brand monitoring is an integral part for the success of any organization. You must be aware that a lot of conversation goes on the web about your organization with or with without your consent. And, it is good if you could monitor all such conversation so that you are in a position to formulate a strategy for building up your brand's image.
Here are some free tools that would help you monitor your brand's reputation:
Google alerts

Google alerts are email updates of all the latest and relevant Google results. These results are based on the type of query or topic specified by you. All you need to do is subscribe to each alert through email and RSS and the alert will track blog posts, videos news articles, and even groups that would notify you of stories, as they happen, for your name, your topic, and even your company.
Blog Comments
Tools like Backtype and coComment helps you monitor blog comments. As and when people comment on various blog posts, citing your name, Backtype will help you find, follow, and share comments from across the web. Whenever you write a comment with a link to your Web site, Backtype attributes it to you.
Social Comments
Yacktrack is a social comment tool that lets you search for comments on your content from various sources, such as Blogger, Digg, FriendFeed, Stumbleupon, and Wordpress blogs. For example, when you comment on a blog, YackTrack will help you locate other people who are commenting on that same blog post and rejoin the conversation.
Twitter Search

With Twitter search, you can locate any instances of your name and decide whether you want to tweet back or ignore them. You can also conduct a search for your name, your company's name, or the type of service you are offering and then subscribe via RSS. Twilert and TweetBeep are tools you can use to receive email alerts.
FriendFeed
FriendFeed is a social aggregator that allows you to take care all of your social accounts, such as YouTube, Delicious, Twitter, blog, and Flickr, by pulling them together into a single (Friend) feed. You can conduct searches on your brand throughout all social networks at once using this search engine.
Social Search
The Social Mention search engine searches user-generated content such as blogs, comments, bookmarks, events, news, videos, and microblogging services and enables you to track mentions of your brand across all of these areas.
After you select the tool/s you would want to use in your brand reputation management system, you must schedule for when you want to check your status. Participating regularly and paying attention to how your brand image is being communicated is one of the ways of monitoring and building your brand's reputation.
Hope that tools will help you in Monitoring Your Brand's Reputation. Please share your suggestions and feedback with us.