Contract Management Software

While many of the established ERP vendors have modules that support Contract Management Software, has anyone got any suggestions on SaaS providers for CMS? My client has a standard customer contract plus many, varied contracts with service providers, key business partners, property leases, software vendors etc.

Core functionality should include ability to:
1. track contracts for compliance, renewal/expiration, commercial/financial terms
2. workflow to move drafts (incl email integration) between parties
3. ability to construct contracts from a library of standard/required terms and conditions
4. document scanning and attachment to customer/vendor record

If the solution has a proven integration with SalesForce.com that would be very good to know.
Ability to manage redline document versioning between parties and e-signatures is nice to have.