Find a Couple's Registry & Wedding Website
Attire and Accessories
Invites and Paper
Not Engaged Yet
Engaged & Proposals
favors if you are doing them
edit: just realized you said decor, guess favors could be decor... a pen for the guest book...are you doing the linens or is the venue providing them, thats decor (right?)!
edit again: i found this website and it seems to be pretty good checklist wise