The biggest players on the market are:
• Google Analytics
• Adobe Site Catalyst (aka Omniture)
• IBM Coremetrics
Note that these are general Web Analytics tools that have a very similar set of features.
There are a couple of very intersting small players popping up that don't offer everything the tools above offer but are very focused and good at what they do.
• Click Tale
A lot of services offer integrated Web Analytics Solutions that are very handy since they have native integration with off site services that may be otherwise hard to measure.
• Blogger Analytics
• Twitter Analytics (currently being rolled out)
• Facebook Insights
• YouTube Stats
A Good Analytics Solution is often a mix of technologies and human analyzes.