myspace and xanga and other community based websites are a great way but they're also very cumbersome. I know many people that are starting their own clothing line and believe it or not panic39 on myspace is headquartered in chino hills california. i live in anaheim but have friends on the east coast and was surprised to hear that they heard of panic39 through myspace.
you can gain a lot of exposure but it's a lot of maintainance if you don't mind that. i don't think advertising a brand name clothing line on a website would be very effective.
Creating a brand name clothing line is very difficult. most celebrities are the ones that come out with well known labels because they already have the exposure but companies like 'not of this world' and 'rvca' have done very well in southern california and have been expanding around the world.
my advice? contact merchants/retailers that may be interested in selling your line and if you have to give them the shirts for free. if they sell you'll most likely hear from them again.
check out notw.com. they're a christian tshirt company with awesome designs. i didn't know who they were until recently when i noticed every single car plastered with their logo in SoCal.
good luck!
