Might be a bit overkill to start, but we started early on with salesforce.com, which provided a good framework that we've grown into. Other CRM solutions like sugarcrm would work too.
Fat Free CRM (http://www.fatfreecrm.com/) is a pretty nice self-hosted, RoR, option. There's an iOS app for it called Senbei, off the top of my head, although it is a little limited.
For the first two I use Kanban: I have one bin for "On Radar" (people I need to send proposals to, etc), and "Followup". The card for each person has their email address and when I should follow up with them