Get datasheets for different electronic components:
Sources for datasheets are:
www.alldatasheet.com
www.datasheetcatalog.com
www.datasheetarchive.com
www.datasheet4u.com
www.datasheetlocator.com
Get different softwares to develope your robot:
>> Assemblers
>> Compilers
>> Simulators
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>> PCB designing
etc
Get a huge collection of ebooks here related to robotics:
>> Humanoids
>> programming
>> Evil genius
>> special types of bots
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get some important resources for Ur bots here:
>> 8051 libraries
>> programs
>> PCB designs
>> AVR resources