Elastic IP + EC2 + Elastic Block for hosting. S3 for backups. I also make judicious use of Mechanical Turk for usability testing.

I also use Google apps for my domain for email hosting (free). I also use Woopra's real time analytics (free).

I have an online store that I'm paying Yahoo Merchant Solutions for. I also pay for an extra line with Vonage for my business line. ($10 a month).

I've used Google Adwords for advertising occasionally.