I normally just buy 10 ounce bars of silver. The reason I do this is because they are much more liquid than 1-10 ounce bars of gold.
I think this will make them much easier to sell on Ebay or whatever, when I feel like the market has topped.
If you have a 5 ounce bar of gold and gold goes to 5k an ounce, that's going to be pretty hard to sell, not many people have 25k in cash laying around.
I normally buy from here: http://www.bullionbourse.com/
Cheap shipping and postage costs, good customer service, and normally pretty fast delivery.