Most atheist I know acknowledge the existence of religions. Based on your comment, I assume that you do not find the topic of religion interesting. However, religion is still a very rich subject with a lot of potential for research. However, in order to do good research, you will likely need a way of classifying and differentiating different religions in the same way we classify different species.
B-Con's comment raises a very interesting question for research. Namely, how is it that so many people think such vastly different belief systems are the same?
Of course, I suppose one's views on religion would be different if one grew up or lives with it being a significant part of one's life. As someone who has grown up with relatively little religion, I am in a position to look at it and be interested in religion as a phenomena.
To use your example, is 'intelligent design' really just another word for 'creationism'. Or, our these two different ideas being supported by different groups of people. If you say that all religion and irrational beliefs are the same, then the answer is a pretty clear yes, they are the same. However, you may find that 'creationism' represents the belief in a Genesis like account of creation, while 'intelligent design' is the remains of the creationism battle, and is founded on the idea that evolution is a non-nonsensical concept and that and that existence is the result of a deliberate conscious action by an intelligent agent. Assuming these are characterizations are true (which they likely aren't), you can then look into how these ideas came about, and look at how influence intelligent design is from creationism. Is it actually being proposed by the same people? Have there beliefs actually changed? Is intelligent design being supported by the children of creationist, because the children can see that biblical creation does not work but still believe that an intelligence is necessary for creation?
On an unrelated note, writing this comment made me curious about the intelligent design/creationism divide. Does anyone here have an insight into what is going on there?