Your portfolio website is a space online where you sell yourself, gain credibility and allow others to view a sample of your very best work (not the latest photos that you think are good right now, but creme-de-la-creme* of your current image collection) It can be just one site/profile where you focus all your work, or a mini network of different sites and galleries aimed at different market segments. It can consist of one or more of the following:
(*cliche justified to emphasise this important point)
1] Just use your profile page on a microstock site
Not really the most flexible option, but it's a baseline for photographers to use, and if you get the opportunity to post a link somewhere online then a link to your profile on a microstock site (via one of your affiliate referral links of course) is one of the options would should consider first. e.g. alongside an image that you post somewhere include a link "buy this image now at Fotolia" to grab a potential buyer. TIP: remember the potential buyer 'wants it simple' they are at least 10 times* more likely to respond to a link that allows them to buy instantly than a piece of text that says "email me for a quote on this image"
*in the microstock photography market (it's hard to measure exactly what the real value would be, personally I think may be 100's of times more likely, if you are interested in web usability then I recommend reading Jakob Nielsens' Alertbox at useit.com
2] Social Network
Google+, Facebook etc, these are a very trendy place to be, there are quite a few photographers who appear to be doing quite well out of promoting themselves here (and that is one of the tricks - the illusion of appearing to be doing well!). Use your social network profile to show off a few of your best images, perhaps create a photo book at blurb.com and do some self-promotion with that too. Setup a page (fan page on Facebook etc.) where you can gather a following of potential buyers. Getting people to 'like' your work is not always easy, the vast cyberspace graveyard of pages and groups that only have one follower or member are testament to that. Probably the best way to learn is through watching others. If you see someone who has a large following then start to analyze why that is? do they have a website? did they give someone away for free? do they provide a useful service?, provide endless updates or just a fee succinct news posts? etc. Once you have a following on your social network you can (subtly) update it with news of your newest images at a microstock agency, or perhaps seasonal posting and 'ideas' at an appropriate time of year. Segmentation is a decision to be made from the very start, some go for a 'catch all approach' while others choose niche areas with tightly focused demographics.
3] Free Photo Sharing
flickr, webshots, picasa, photobucket, panoramio, etc you can share your images for 'viewing only' on dozens of photo share sites around the net, flickr I would recommend just for the sheer size of the audience, disadvantage of many of the sites is that they are not really aimed at the photo buyer. They are an easy place to start getting your work shown and receive feedback from the public (they might not be professional photography critics, but these are the people who will view your images if they are used in a design). The comments are often trite, and this is certainly the place for those photos of kittens and flowers if you have them; understand the audience and these 'galleries' can certainly attract mouse clicks for you.
4] Paid Photo sharing / Professional portfolio
You have to pay for webspace, but the advantage here is that you are uploading to a site specially designed to allow you to promote your work, some sites even blur this concept with one of selling images and allow you to sell your portfolio directly. I feel that selling images directly from your portfolio is perhaps not the way to go, you will have to do a lot of work to convince a buyer that you are a genuine professional operator (but slick looking websites like smugmug can help with that). Unless you have lots of time to spare, then best to leave this marketing to the microstock site themselves, and remove your need to deal with customer problems and get involved in marketing and advertising.
5] Your own website
Setup your own custom website or blog and make it look good! If you can't make it look good - and when I say good, I mean impeccable in every aspect, then see one of the above options and don't waste your time. Setting up a website involves more work than anyone who first has the idea of doing it can imagine. Again if you do already have a blog perhaps on an unrelated topic, then it might still be worth linking with one of your affiliate referral links. Many people with personal blogs write small articles about their microstock ups and downs in an effort catch a few photo buyers along the way. Your website can be as little as a page with your contact info and a few sample photos all the way up to a full-fledged gallery, perhaps with your own photography e-commerce solution
Self Promotion Ideas:
Print the address of your portfolio website on business cards (even if like me you only ever give them out when you are out shooting it's always worth having a business card, look professional. Include one link (exactly one, not an explosion of all the links you can think of!) in your email signature, or on any printed promotional items that you might make.
If you have more than one portfolio site/space/gallery (which I recommend if you cater for more than one market) then theme each one to a specific side of your talents, keyed to the style of the location of that gallery. Example: have a relatively generic portfolio gallery site which you include in your email signature, but link from there to some of your more specialist portfolios "see more of my food photography on flickr.com" or "see more about my festival and event photography at myspace.com" or "see more of my travel stock images at panoramio.com".
For more photography marketing tips read promoting your portfolio