Here is a sampling of links to websites representing a variety of forms of creationism, including young-earth, old-earth, and "intelligent design" creationism.

Answers in Genesis
A young-earth creationist ministry which operates a Creation "Museum" in Petersburg, Kentucky.

Access Research Network
Promoters of "Intelligent Design" Creationism.

Center for Science and Culture (Discovery Institute)
The "intelligent design" think tank associated with the Seattle-based Discovery Institute.

Creation Ministries International
A young-earth creationist ministry, renamed when Answers in Genesis underwent a schism in 2005.

Creation Research Society
The "research arm" of the creation science movement. Young-earth creationist articles are published in the journal CRS Quarterly

Institute for Creation Research
A major center of young-earth creationism.

Reasons to Believe
A Christian ministry that favors the "old Earth" view: the ancient age of the universe and Earth is accepted, but not biological evolution.

See also this extensive list of creationist websites maintained by the Talk.Origins Archive (not itself a creationist website).
List of creationist web sites