Favicon
I think it’s a good idea to regularly change your favicon to remind customers that you exist just a click away, for if they have their bookmarks displayed visibly as buttons I do this, and one of my links on my Bookmarks Toolbar is Amazon.com, and I display it as an Icon only. Recently they changed their Favicon enough to draw my attention to it (It changed the appearance of the environment I look at every day) but not so much as to appear unfamiliar. Google has been doing this with their logo. The familiarity of the change added, I think, to their overal public image signature. I think it might work because it links the icon (and thereby the business [like a pointer]) to both your present awareness, but also in your memory, so your thinking about the icon (and thereby the business) from two different perspectives, using two different processes of your brain.
Come to think of it, Weather.com does something similar but with a diminished frequency- I think it might be that they change their banner and theme seasonally. I can’t remember what they are now or what they’ve recently been though. This tells me that it’s likely that one can build an immunity to this tactic- still it can’t be the only trick in your bag. I think that you’ll reach a point where you filter things like that out of your comprehensive view. Who knows-