What are some alternatives?
When comparing Sparta and Mustbin, you can also consider the following products
Close - A CRM with built-in calling, SMS, and email
Index - Organize everything
SalesWise - A gorgeous launchpad for sales people
InTouchApp Firefox Extension - Save contacts & data from websites to your phone
Hoopla - Your public library at your fingertips.
ArchiviCo - An easy way to store your important documents