Everyone responsible for a product portfolio should read this blog entry from the Silicon Valley Product Group. I can't really add much advice to this excellent post - great solid advice.
One company that has really got this right is Citrix Systems - they have focused on four main products ("the four platinums"), reduced their investment on secondary products, and end-of-life non-performing products. They publish the best product lifecycle matrix I have seen at http://www.citrix.com/site/SS/supportThird.asp?slID=5107&tlID=5110 - very easy to understand.
This is especially important post acquisition - at Blue Coat we moved quicly to end-of-life Packeteer products that were not moving forward. Although there was revenue attached to these products, customers and partners generally reacted well to the plan that was presented to move forward (there will always be a few difficult customers). Everyone appreciated that Blue Coat was quick to create certainty and presented a transition plan for Packeteer customers using EOL products.