• The F# Home Page. This is the official home page for F# at Microsoft Research. Quite a bit of information can be found here, including download links for the F# distribution, the F# manual and the F# library reference.
• hubFS. The forums at hubFS are a gold mine of information. This is where the F# authorities (like Don Syme himself!) answers questions.
• F# Wiki. There are some great articles and tips here. Hopefully, this will expand as the interest around F# increases.
• The F# Journal. This subscription-based online journal is maintained by well-known F# authority, Jon Harrop. The content is quite good, but unfortunately, the subscription is quite expensive. Currently, a six-month subscription is priced at £59. At today's exchange rate, that's approximately $122—an amazingly hefty price for an online journal. (For comparison, consider that an online subscription to Cambridge's Journal of Functional Programming only costs $135 per year for individuals.)
• Don Syme's Blog. Don Syme is the creator and principal maintainer of F#. If you're learning F#, you must read his blog. It's a requirement. Don's book, Expert F#, is available for pre-order and should be shipping sometime in Nov./Dec.
• Robert Pickering's Blog. Robert Pickering is a heavyweight in the F# community. In addition, he is the author of the excellent Foundations of F#.
• Jomo Fisher's Blog. Jomo is a member of the new F# team in Redmond. His blog contains many interesting articles that examine F# through the lens of C#.
• Tomas Petricek's Blog. After spending some time in the hubFS forums, I've quickly grown to appreciate the expertise of fellow C# MVP, Tomas Petricek.

If I've forgotten any important resource links for F#, feel free to list them in the comments.