Wi-fi
Theoretical speeds
802.11b – 11 Mbps (2.4GHz)
802.11a – 54 Mbps (5 GHz)
802.11g – 54 Mbps (2.4GHz)
802.11n – 600 Mbps (2.4GHz and 5 GHz) – 150Mbps typical for network adapters, 300Mbps, 450Mbps, and 600Mbps speeds when bonding channels with some routers
802.11ac – 1300+Mbps (5 GHz) – newer standard that uses wider channels, QAM and spatial streams for higher throughput
Actual Average Speeds
Below is a breakdown of actual real-life average speeds you can expect from wireless routers within a reasonable distance, with low interference and small number of simultaneous clients:
802.11b – 2-3 Mbps downstream, up to 5-6 Mbps with some vendor-specific extensions.
802.11g – ~20 Mbps downstream
802.11n – 40-50 Mbps typical, varying greatly depending on configuration, whether it is mixed or N-only network, the number of bonded channels, etc. Specifying a channel, and using 40MHz channels can help achieve 70-80Mbps with some newer routers. Up to 100 Mbps achievable with more expensive commercial equipment with 8×8 arrays, gigabit ports, etc.
802.11ac – 70-100+ Mbps typical, higher speeds possible over short distances without many obstacles, with newer generation 802.11ac routers, and client adapters capable of multiple streams.
Powerline Adapter
Up to 1200 Mbps (theoretical).
http://www.amazon.com/gp/product/B00S7NJWOM?psc=1&redirect=true&ref_=od_aui_detailpages00
USB and Other Types of Connections
Theoretical speeds from slowest to fastest
USB 1.1 = 12 Mbit/s (1.5 MB/s)
Firefire 400 = 400 Mbit/s (50 MB/s)
USB 2.0 = 480 Mbit/s (60 MB/s)
FireWire 800 = 800 Mbit/s (100 MB/s)
USB 3.0 = 5 Gbit/s (625 MB/s)
USB 3.1 = 10 Gbit/s (1.21 GB/s)
eSATA = Up to 6 Gbit/s (750 MB/s) right now as it depend on the internal SATA chip.
Thunderbolt = 10 Gbit/s × 2 (2 channels), 1.25 GB/s × 2 (2 channels)
Thunderbolt 2 = 20 Gbit/s (2.5 GB/s)
Thunderbolt 3 = 40 Gbit/s
List of various device speeds
https://en.wikipedia.org/wiki/List_of_device_bit_rates#Peripheral