Straight from Ebay's own listing policies:

*********
Summary: eBay listings can only be used to
 facilitate the sale of the listed item. Listings 
can't refer to or promote the seller's individual 
Web site, off-eBay sales or other businesses. On 
the eBay About Me page, however, the seller may 
promote their individual Web site or business.
**********

So as long as the link is on your About Me page, 
you are fine.

^_^

JP (who used to get confused by this, too)