hi i have a eos 350D
and i have nvr taken out my lens before not once.(only time was when i got the cam nd to mount lens)
i am not sure if this is dust but it looks like it.
the higer the aperature the more visible the spot is.
its dust, and nothing to panic about... you can either send it back for cleaning (probably a fee) or you can get a visible dust brush to clean it, or blower to blow it off, or sticky tape to remove it. search the forum for more details.
dust on lens won't be visible, cos anything on the lens, unless very prominent on the rear lens, is not visible cos of the minimum focusing. put a finger in the front of your lens and see, then u think, will a small dust be visible?
anyway, send for cleaning, you will still get it later, cos dust can also get in from the side, as the bodies are not dust proof as well.
yr camera and kit lens are not weathered sealed so it is possible for dust to get in. especially so if you are shooting in dusty enviroment.
just get a blower (clean one) and blow the dust off. canon will charge you S$21 for cleaning. warranty do not include sensor cleaning. i sent mine in for cleaning as the dust was stuborn and cannot be blown off.
however, like most had said, dont need to panic, can just clone off in ps.