Earlier today Philip Bloom posted about affordable monitors for the 5D, not quite as nice as the TV Logic monitor I posted about a couple of days ago but certainly a lot cheaper. But you can never forget your cables.
For awhile now I've been buying all my cables from monoprice.com. Monoprice is an amazing resource. Have you ever had the mooks at Best Buy try to sell you an HDMI cable for $120... how TOTALLY crazy do you have to be to pay that kind of money for a cable. Recently I installed an HDTV and needed to hook it up to several HDMI sources... I went to monoprice.com and was able to by 10' HDMI to HDMI cables in various colors for $4.74 each.
Philip recommended a 6' cable for $15 from B&H. However, you probably don't need a 6' cable. How about a 3' HDMI-mini to HDMI from monoprice.com for $4.05 and while you're at it buy 2 and get a price break for $3.71 each and have a spare in your bag.
At any rate... definately check out www.monoprice.com, an amazing resource.