Go to National Semiconductors **broken link removed**, search for the part you're looking for and then a page will appear with the description of the part/parts and with info about whether free sample is available or not. Before asking for the sample you have to register yourself which is free. You can ask for a maximum of 5 types of samples/week. They send one for each type every week.
thank two friends,but I had knew Ns and TI two web offer free sample,but also I know **broken link removed** can offer free sample too.if can tell me the other web. NS and MAXIM is very easy for request sample,TI is difficult.
Most of the other sites don't offer free samples. But if you send e-mail asking for some, a few will respond. Twice I asked Sharp by e-mail to send me two Photodiodes. They sent both the times.