I am a .NET webdev using ASP.NET, C# etc... I \"learned\" javascript in college 5+ years ago and can do basic jobs with it. But I wonder if it is useful to become proficient in
Yes, absolutely you should learn JavaScript if you are doing web development. I highly recommend JavaScript: The Good Parts, by Doug Crockford. And, JQuery is a great framework to use (this site uses it) -- it kind of depends on what you are trying to do -- YUI and ExtJS are also very nice.