125kHz RFID Readers and Tags which support the EM40XX/EM41XX chipsets are the most commonly used in the 125kHz frequency range and are likely the least expensive technology.
Look for EM41XX or EM40XX compatibility when purchasing either the RFID Reader or Tag.
Also make sure you order a reader with the correct interface for your design. RFID Readers are manufacture with several interface options, with the Wiegand26 interface being the most common, particularly with commercial units. Be aware that the Wiegand26 interface is NOT compatible with either the RS-485 or the RS-232, which are most likely the second and third most common interface available. There are also other variations of the Wiegand interface available, including Wiegand34 and Wiegand42. Magstripe, Clock & Data and TTL Level Asynchronous Serial are other possibilities.
For a hobby project, where the RFID reader will be located in close proximity to the microcontroller, I would recommend either RS-232 or TTL Level Asynchronous Serial interfaces.
The Innovations ID-20 is a nice RFID Reader, I've actually use an ID-20 for prototyping/testing code:
**broken link removed**
A few Online Indian RFID Sources:
Simple Labs - India
Rhydolabz RFID Tags and Readers - India
Element14 RFID Tags and Readers - India
Probots RFID Tags and Readers - India
Hope the info helps with your endeavors,
BigDog