is it possible to use 8051 to do some voice recording application. and how? i.e *recording mic-->AMP-->ADC--> 8051---> serial eeprom. *Playback Serial eeprom--> 8051--> DAC---> Speaker. are there any referance material in the web?
Yes; you seem to have the process outlined reasonably well. All you have to do now is design and build the hardware and software :) Atmel makes some 8051 derivatives with built-in MP3 decoders. Those could perhaps be of interest. Searching for VoIP will lead you to discussions of the G.723 and G.729 voice compression standards, which also might be of interest. There's probably a device to do that compression by now, though I don't know of one specifically. You'll probably want a part with an extended memory space. 64k doesn't last long when you're sampling sound, even when it's compressed.