Salesforce Customisation

Hi. I'm looking at various CRMs including salesforce to manage my sales workflow and there is some customisation I would like to be able to achieve.

There are 3 things missing from the default salesforce installation I think which would be great to integrate.

Firstly, for any contact/lead/organisation, I'd like to be able to link to other known contacts/leads/organisations. When I call a new lead, it's important for me to know who else on my system they know as it instantly creates an affinity with them.

Secondly, I'd like to be able for any contact/lead/organisation be able to see a list of other contacts/leads/organisations who are close by, based on geolocation I suppose generated from their address.

Finally for any contact/lead/organisation I'd like to be able to see similar contacts/leads/organisations based on tags. I suppose tagging is possible in salesforce?

If I add some of this info for a contact, I'd also want to be able to see it for that contact's organisation too. So have it propogate up.

I hope that all makes sense. Let me know what you think and what sort of price it might cost.

Many thanks

Matt