On ebay, i've been charging 5 bucks flat for priority mail with delivery confirmation. insurance additional if desired.
otherwise, 2-3 bucks for first class, usually including DC. For one or two items, First Class is cheaper than, or not much more expensive than, Media Mail, and gets there quicker.
Anyone else have your PO tell you video games don't count as 'media'? last time I sent something [priority, so it didn't matter to me], there was someone in the PO sending Media Mail, and the clerk specifically asked 'It's not a video game or game cartridge, is it?'
You can print Priority mail postage labels, including free Delivery Confirmation, from the USPS Click/n/ship website. The labels print on regular 8.5x11 paper. No need to download anything, it's an on-demand service. Plan ahead, and order priority mail boxes and tape for FREE from USPS.com as well. [I've got more boxes than I'll ever use, but I use them only for shipping Priority, so I don't feel guilty about it.]
i used to like Stamps.com when I was selling a lot on Half.com, but they went up from 1.99 a month [I would pay that] to like 14.99 a month [I would NOT pay that.] Plus postage costs of course. it was quite convenient, you could print postage and mailing/return addresses right from your own printer, and they'd get there quicker. But a 653% price increase was too rich for my blood.