I have just been introduced to the idea of eportfolios myself and found that a website recommended to me, Dr. Helen Barrett's Electronic Porfolio ,to be helpful. I have just begun an eportfolio and have used Google sites. So far, so good.
I think this is a great idea - if for no other reason that it provides a central location to keep track of one's (developing) professional skills. Plus, you never know when it might help you land your dream job (this is what happened to me - I had an administrator cold click on my online portfolio and subsequently received an invitation to an interview and eventually the job).
Depending on your tech skills, I'd might recommend purchasing a domain name and hosting (this can be super cheap - I go with lunarpages.com for $5 a month) and creating your own website that serves as a portfolio. I definately recommend going with something modern (we educators sometimes have a tendency to design our websites as if it's still 1999) - see something like OSWD for free templates you can tweak.
Another idea is to install wordpress (which has gobs of professional looking templates) and use that as your portfolio. It's fairly easy to upload docs and write pages/post.
As with most things technology, there's a 1/2 dozen ways of doing this!
I just want to say these are all very helpful ideas for a new teacher. I am in the middle of a career change program to teach middle school. I am quite new to discussion boards and blogging and am realizing there are a wealth of great ideas. Thank you!