I'd definitely recommend http://rimuhosting.com http://rimuhosting.com I know of at least 1 YComb startup that has used it in the past - and we're using it now

I'd definitely recommend http://rimuhosting.com http://rimuhosting.com I know of at least 1 YComb startup that has used it in the past - and we're using it now. I've personally been hosting with them for 2 or 3 years now and it's hands down the best virtual hosting I've used (compared with 4 others I've tried). Other friends are using Amazon EC2+S3 for scaling needs (on the fly load-balancing). Haven't used it myself, but I only hear great things.