Okay... I have a Canon EOS

Okay... I have a Canon EOS 400 with the standard 18-55mm lens that comes with it.

My brother in law has asked me to take his wedding pictures with it, just wondering if anyone could recommend the kind of lens I should use.

I have seem various ones with different ranges and image stabilizers and ones called macros, but am a bit lost as to what a macro lens it... It is also seems to come in a fixed mm, like 50mm macro aaarghh... A bit confusing for the novice

WILL THIS HELP?
http://www.digital-photography-school.com/choosing-a-lens-for-wedding-photography-stepping-into-wedding-photography-part-2

i've done a lot of work with photography and come to realize one thing, lighting matters more than anything. Adequate lighting will make your novice shots look pretty pro.

One thing to do is configure your camera to have a proper white balance prior to shooting, this will help a bit.

For shooting people on the fly you'll need a flash, unless you're lucky and the wedding is outside on a nice sunny day. I'd suggest a fairly high powered flash since you'll need to stay some distance back from the ceremony, this particular area I do not have much expertise in. All i can really say about flashes is to make sure they are producing solid white light. With product photography i use 4 bells and 5500k lights in each to light my stages. bhphoto has some good deals usually.

Good luck!