well one diea is to search on the manufacturer of the component, if you know what you are going to buy. i use www.questlink.com wich is a quite big database. there are lots of other websites.
**broken link removed** Analog Devices http://www.linear.com/about/site.html Linear Technology **broken link removed** Maxim Integrated
**broken link removed** Microchip **broken link removed** Motorola **broken link removed** National Semiconductor
**broken link removed** Rohm
**broken link removed** Texas Instruments