Make a bundle with some products and share the url on your newsletter, facebook, etc. When the customer clicks the url they will be automatically taken to a pre-filled cart with your product bundle.
You can combine this with a juicy discount, just add a shopp discount (percentage off, amount off, free shipping, or buy X get Y free) with the condition that your bundled products are in the cart.
This plugin adds a shortcode which you can insert on a page, accessing the page will then automatically take you to a pre-filled cart.
Get the Shopp Cart Bundler Plugin today and start bundling your products!