SCM SCL3711 Fulfilled by Amazon. Price: $38.95 

Identive SCM SCL3711

Openwrt/YunOS has very good lib to support NFC, unfortunately it is out date.

Install updated software:

cd /mnt/sda1
wget -O  nfc.tar.gz https://www.dropbox.com/s/moyx9otp7fpptzn/nfc.tar.gz?dl=0 --no-check-certificate
tar -zxvf nfc.tar.gz

cd nfc
opkg install libnfc_1.7.0-1_ar71xx.ipk
opkg install libnfc-bin_1.7.0-1_ar71xx.ipk
opkg install libnfc-examples_1.7.0-1_ar71xx.ipk
opkg install libfreefare_0.4.0-1_ar71xx.ipk
opkg install libfreefare-examples_0.4.0-1_ar71xx.ipk

Testing with mifare card:

root@Arduino:/mnt/sda1# /usr/bin/nfc-poll
/usr/bin/nfc-poll uses libnfc 1.1.0-30-ge81b29b
NFC reader: SCM Micro / SCL3711-NFC&RW opened
NFC device will poll during 30000 ms (20 pollings of 300 ms for 5 modulations)
ISO/IEC 14443A (106 kbps) target:
    ATQA (SENS_RES): 00  04
       UID (NFCID1): d4  b0  48  2f
      SAK (SEL_RES): 08

 The User space applications come with libs:

/usr/bin/mifare-desfire-access
/usr/bin/mifare-desfire-write-ndef
/usr/bin/mifare-desfire-read-ndef
/usr/bin/mifare-classic-write-ndef
/usr/bin/mifare-desfire-create-ndef
/usr/bin/mifare-desfire-ev1-configure-ats
/usr/bin/mifare-classic-read-ndef
/usr/bin/mifare-desfire-ev1-configure-default-key
/usr/bin/mifare-ultralight-info
/usr/bin/mifare-desfire-format
/usr/bin/mifare-desfire-ev1-configure-random-uid
/usr/bin/mifare-desfire-info
/usr/bin/mifare-classic-format
/usr/bin/nfc-mfultralight
/usr/bin/nfc-mfclassic
/usr/bin/nfc-list
/usr/bin/nfc-emulate-uid
/usr/bin/nfc-anticol
/usr/bin/nfc-poll
/usr/bin/nfc-relay
/usr/bin/nfc-relay-picc
/usr/bin/nfc-dep-target
/usr/bin/nfc-emulate-tag
/usr/bin/nfc-emulate-forum-tag4
/usr/bin/nfc-dep-initiator

 The reader is SCM SCL3711: