What do I do with all my old block erupters? I'm making like nothing off these guys and am looking to use them for something else.  I guess these ASICs are designed for SHA-256 hash function based cryptocurrencies.

Try to mine Terracoin?

cryptocurrency list:
http://dustcoin.com/
I use mine in "lottery mode" as I call it. 

They don't really consume too much energy, so I just let them solo mine. Big chance will turn out to be nothing, but with some luck they will ever find a block and cash in 25 BTC.

How low the chance may be, it's still a lot higher than winning the ordinary lottery and way cooler :)

EDIT: A quick calculation of your odds.

The current (2014/01/24 23:07) chance of a hash to be a winning hash is 0.0000000000000000001061272725905534506860017351925762341. Then the odds of winning each day are for one block erupter USB of 330MH/s

0.0000000000000000001061272725905534506860017351925762341 * 330*10^6 * 60*60*24 = 1 / 330480.1

So one chance in 330,480 each day or one chance in 905 a year (of course, changing difficulty has to be taken into account).

Let's take the Powerball lottery as a reference as Earlz mentions, it has odds of one in 648,975.96 to win $10,000 one in 5,153,632.65 to win $1,000,000.

So, every day you have double the chance to win 25 BTC than you have to win $10k, which is less and costs you probably a dollar or two to enter.