I have some old layouts, and I would like to sell them, are there any popular online auctions service?
Rin, guessing not, but maybe, who knows.
(1) You could trying to sell them on webmaster auction sites, but normally webmasters are not the in market for site templates. Examples of webmaster auction sites would be: forums.digitalpoint.com and marketplace.sitepoint.com
(2) A big template site like monstertemplates.com likely wouldn't be interested in them either.
(3) Which leaves the target market for your templates with consumers looking to buy templates, which would likely rather deal with a large company. Guessing the best site might be eBay using PayPal would be the best way to reach consumers.
Questions that are likely to be asked are: Have any screen shots? More Info on how much you expect to make? Info on copyright of any graphics used? If the templates are standards complaint? Which browsers they work in? Etc.
I would suggest checking out Theme Forest, They have alot of stuff there and a very active user-base.
Theme Forest Author Program: http://themeforest.net/wiki/selling/author-selling/author-program/