Can someone provide a good overview of the differnces of the Catalysts 3750 Cisco switch versus the Cisco 6500 Blade switches please?

to add......
3750 = Core switch/router for smaller organizations
3750 = edge switch (to each desktop) for larger organizations
6500 = core switch/router for larger organizations (and should be accompanied by edge layer switches, ie 29xx, 36xx and 37xx switches).

6500 is modular, you can add multiplesupervisors (4 failover), cards (FWSM) for firewall, wireless (WiSM) etc You can add functionality centrally, on one box.
Is should be used as core switch for big organization, and is a good investment as it will be EoL after many many years...

3750 can be used as L3 core switch to Small/Medium-Size organizations. It has stuck capabilities, but after all is just a L3 switch. Has almost everything you will need. Additional functionality can be added to separate routers etc

If you plan to grow fast, go for 6500 ;)

3750 comparison:
http://www.cisco.com/en/US/products/hw/switches/ps5023/prod_models_comparison.html
6500 comparison:
http://www.cisco.com/en/US/products/hw/switches/ps708/prod_models_comparison.html

6500 modules:
http://www.cisco.com/en/US/products/ps6526/
http://www.cisco.com/en/US/products/hw/modules/ps2706/ps4452/
and the list grows...

Also consider your future needs versus cost. While the 6500 comes in various size 6503, 6504, 6506, 6509 and 6513 the 3750 can be stacked to meet the density you need. This may help to lower the inital costs. Consider as well that if you need a more robust functionality in a single platform the 6500 series is difficult to beat.

A good answer