The importance of having your own website can never be stressed enough. This means something like www.bandname.com as opposed to a simple page or two on someone else’s domain. Web-space is cheap and plentiful, if you want to be perceived as professional, you should start with your website. In the process of building your site you will also inadvertently put together the materials you need for your press kit.
Pictures, press clippings and audio are a must. At least one band shot and a few handfuls of free, downloadable, full version songs. Your press should be current; no one really cares if the Osh Kosh Herald wrote a review of your first emo-core band, three years ago. You should also have bio info on the band and its members, a page for posting tour dates and your contact information on EVERY PAGE. Lastly, fans should be able to sign up for your email newsletter directly from your front page.
It is crucial that you maintain your site, add new things to it, and change it around. Tour dates should always be kept up to date and old dates should be archived but viewable. This is your window to the world and when people look in they are more likely to listen to your music if they like what they see and hear right away. If you want to put a music player on your site, you should let the visitor turn it on. Having a music player start up suddenly when surfing at work or in a public place can be annoying, especially if the volume is turned up too loud.
I would also consider providing a track or 2 that people can download for free. It sometimes takes time for a song to grow on you and you will have a better chance of being remembered if that person has it on their mp3 player.
Also include links to all your social networking sites.
Useful web hosting sites
Amazon S3 Stores your MP3s and makes it easy to sell them through your own site
BandZoogle Build a band website that does more -- sells music & merch, syncs with your social networks, and puts you in front of more fans. No web design skills needed!
FourFour FourFour is a website builder and web host for Musicians. it has built in templates, Music players, Online stores, and more.