Reputation management and reputation monitoring are hot topics in 2008 and there are a whole host of resources that offer cost effective ways to manage your brand online.
The newest resource on the list is this online reputation management ebook - priced at just $19 it's a great way to find out everything you need to know about the subject.
Another interesting tool is the Reputation Monitor from Distilled which offers a free trial so you can see how it can monitor your brand.
If you are new to the subject then I suggest opting for a free trial to one of the services above and using Google Alerts at the same time to compare features.
After a month you can then decide how much you want to invest in tracking your reputation and choose a service that fits your needs.