There are diffrent tools to address different needs. if by trending you mean Conversations, SPAN, Netflow and other traffic insight details, you would probably want to use Cisco Prime Network Analysis module.
Cisco® Network Analysis Module (NAM) is a product that provides advanced network instrumentation and allows network administrators, managers, and engineers the ability to get a variety of detailed metrics from the network. NAM offers a versatile combination of real-time traffic analysis, historical analysis, packet capture capabilities, and the ability to measure user-perceived delays across the WAN as well as analysis of voice-over-IP (VoIP) quality.
For more details please check :
http://www.cisco.com/en/US/products/ps5740/Products_Sub_Category_Home.html
http://www.cisco.com/en/US/prod/collateral/modules/ps2706/white_paper_c07-505273.html
Apart from cisco's Tool, I am aware of InfoVista for this purpose. Other community members may provide more insight on Tools outside Cisco.
-Thanks
Vinod
**Rating Encourages contributors, and its really free. **
-Thanks
Vinod
**Rating Encourages contributors, and its really free. **