The theory of intelligent design (ID) holds that certain features of the universe and of living things are best explained by an intelligent cause rather than an undirected process such as natural selection. Intelligent design theorists engage in an effort to empirically detect whether many instances of "apparent design" in nature are genuine design (the product of an intelligent cause) or are simply the product of an undirected process such as natural selection acting on random variations.
ID is different than creationism. Creationism is focused on defending a literal reading of the Genesis account, usually including the creation of the earth by the biblical God a few thousand years ago. Unlike creationism, the scientific theory of intelligent design does not have within its scientific resources the ability to discover the source of design. Honest critics of intelligent design acknowledge the difference between intelligent design and creationism. University of Wisconsin historian of science Ronald Numbers is critical of intelligent design, yet according to the Associated Press, he "agrees the creationist label is inaccurate when it comes to the ID [intelligent design] movement."
An individual might be a "creationist" in the sense described above and be very enthusiastic about intelligent design. Why? Because such a creationist might recognize that the theory of ID is supportive of the idea of a designer, who they would identify as the God of the Bible. But there are also those who support the theory of intelligent design who subscribe to other faiths (or who accept no religious faith at all). Non-religious supports of ID may simply remain agnostic about the source of the designing intelligence.
How bright is the future of intelligent design? Despite what you hear -- or don't hear -- from critics (especially those in the media), the past 5 to 10 years have been a boom period for ID research. There are now over 50 peer-reviewed scientific publications that document this progress. The article How Bright is the Future of Intelligent Design? summarizes recent advances in ID.