Plaxo and linken are great and easy to use. You can upload your contacts, information about yourself, your resume and what you are doing. I think this is the way of the future and I like the idea of being able to have it all together. I can go to just one place for all my stuff. Also, other people can see what is happening with me.
A personal website is fine, but I think it may be difficult for others in the same field to find you. It seems easier to go to a site like plaxo and you can see everyone there, the website is already up and running you just add in your info and you are off. A personal website would be great, but it takes more work and I would be worried the right people would not see it.
I find this social networking fascinating and fun to work with. It makes life a little easier to know about all the sites and be able to chose what works best for me.