Out of the box, you can set a base rate of a product (the price for one), and then a "volume" discounted rate when multiples of that item are purchased.  (ie. $5.00 s/h for the first and $3.50 s/h for each additional item of that product)

There is also a modification in the support forums, on setting up a store base rate.  This way, you can simply charge a store rate for the first item, and then add on the cost of individual products.

(ie.  Set a base store rate, and then have individual product rates added onto that)

http://www.markettheme.com/for…..-the-first

Also, if you wanted to edit a few lines of code — you could set things up to have a flat rate based on cost of order. 

A few months down the road, we're looking at expanding the shipping methods as well.

Yes, you would approach it in the same way, except you just wouldn't add on the item rate.  Rather than putting in

it would just be this instead

 (or whatever your flat rate is)