I would suggest HostGator.

I've used them for the last several years (VPS, Shared & Re-seller)
Why I recommend them -
1 - Their servers work, and work well. Often I see load times at 0 or 0.1. I never have to override PHP settings or crazy .htaccess changes to make C5 / Pretty URLS work.
2 - Their tech support is awesome. They use WHM and CPanel. They have online chat, phone and email (ticket) support. They are fast to respond, and they've even helped me work through some script issues.
3 - Pricing - Not bad at all. Their VPS is a little higher than some others, but the support is worth it. Their shared / reseller etc., are great values.
4 - I've used them as our host recommendation for budget minded clients for 2 different agencies.
5 - I've used them for over 5 years. They've never let me down. I had more downtime at dreamhost in one month, than hostgator in 2 years.
Here's a 25% off coupon if you want - C5ThePhilM
And here's post where I talk a little about VPS with several businesses.http://www.thephil.net/blog/vps-for-concrete5-how-to/...

You can always check out our latest recommendations here:
http://concrete5.org/hosting

(clicking a link there and signing up does help the project btw, thanks!)

We've had a lot of luck with Web Hosting Hub at the top.

One of my clients is very happy with her inmotion hosting vps account.

Pacific Host is pretty good also.