http://www.evercontact.com/blog/how-to-fastest-way-to-add-contacts-leads-in-salesforce-evercontact/
Works with other services.
Works with Gmail or Outlook.
Scans email coming in and checks to see if their details has updated, and then lets you know about it to update it in Salesforce.
I use Evercontact in Outlook and it is fabulous. Not sure I would pay the $13/user/month though.
About the only option for mac and/or Gmail users in this list.
http://www.cirrusinsight.com/features/#feature12
Works with Gmail Signatures.
http://www.egrabber.com/addressgrabber/salesforce/
$99.95/year
Works with other services.
https://appexchange.salesforce.com/listingDetail?listingId=a0N300000016bAdEAI
Create Lead, Contact, Account.
Free as the old fashioned Windows App, but there is a new app by RingLead that makes it fully Salesforce integrated.
Their Profiler tool is fabulous, and this is based off their Profiler tool.
Windows App
https://www.copy2contact.com/c2c-salesforce/
Windows App
http://signusapp.wordpress.com/
Uses Salesforce Token authentication.
Doesn't seem to have much customisation for Salesforce.
I am not sure about this one.