You might want to look on the Web, Software & Technology Group for some insight. There's a number of good systems out there. Here's a link to a recent discussion:
Creator of Vacation Props, an innovative iPhone/iPad app to manage vacation properties and quickly respond to inquiries
Like Jennifer said above there are many systems out there.
Here are a few great systems I have persoanlly used for running my business (www.findyourbreakaway.com) That you might find helpful.
www.nutshell.com - Great CRM and very easy to use with amazing reporting tools and email funcationality. Syncs with google apps and is very easy to track sources of leads to measure ROI from marketing. Very affordable as well.
www.salesforce.com - Great CRM as well but a little more pricey. I used it for a while before switching over to nutshell. Probably one of the more popular CRM's around for larger companies.
I'm not sure how your business is set up. But these might also be good options for you to consider.
Feel free to email as well if you need any additional help.