You can use Delicious, Digg, Reddit, Stumbleupon and similar social bookmarking websites to share your designs and design pages.
Use services such as Twitter, Identica, Icarus and Friend Feed to notify your friends about your designs. Make your postings short and relavant.
You can use social networks such as Facebook, MySpace and Orkut to promote your designs. Some of these networks lets you create "Pages" or "Groups".
Social Design Networks
There are also there are special designer networks such as DeviantArt and Flickr, make sure to use them as well! You can search online for more networks.
AddThis / ShareThis
You can also put a Share / Add This button to your webpages and get a custom code at addthis.com or sharethis.com . This includes everything.
You can send email to your friends about your newest designs, be sure to notify your friends if you are winner. You can include your profile URL to your emails as a part of your signature.
Join online forums and talk about design, make sure that your webpage URL is included as a part of your signature.
You can join some of the relevant email groups and post your designs, make sure that your postings are relevant.
Online Design Magazines
Communicate your latest designs to the online design magazines, reach editors and send your portfolio or latest piece, you can also send your profile URL.
Remember to make updates every once in a while.