As ever, the answer is some variant on 'depends what you want to do with it'. If it's sales, something like Pipedrive, which returns JSON from their API will w

As ever, the answer is some variant on 'depends what you want to do with it'. If it's sales, something like Pipedrive, which returns JSON from their API will work well with Python. If it's more general contacts, I've also used Highrise (the 37 signals one), which has pretty crappy security/user permissions, but is nice to use, and Insight.ly, which is reasonably extensible as well, which I mainly use as a contact book/repository for conversations with people I meet. THe others can be used like that, but I found inslightly a bit better for multiple non-technical users.