Ask HN: Gadget/service recommendations to make an office mobile

I run a niche e-commerce business and am making my office mobile. What gadgets and services would HN'ers recommend to make it easy to work effectively from just about anywhere? I've started to make the transition, so I'll start: - eFax and a VOIP number of course - Neat Receipts Scanner: super portable, scans any document - NitroPDF: editing PDFs is useful when you need to fill out documents and forms without the use of a printer or scanner - Online BillPay: service offered by most banks so you can mail checks online - DropBox - Anyone have any experience with remote inbound mail services like earthclassmail.com? - I love having a second monitor but would never lug one around. Anyone have any suggestions? Is there a good tablet to rig up as a second monitor?