My company uses Salesforce.com, like Rubicon mentioned. You pay a monthly fee per user, and you won't have to worry about managing the equipment or software at all.
I've built some web based database-driven apps before, and I'd still recommend looking at something like Salesforce.
You might also want to take a look at ACT! Web. I don't know a lot about it, but it looks like something you host yourself if you want to go that way.
http://www.act.com/products/web/index.cfm