Popular Speed Test Sites:
These sites don't give consistent results. Below are the results of 3 tests on each site at 2 AM with a linksys WRT160NL wireless-N router to a MacBook with an 802.11n wireless interface thru two walls. Site Results

speakeasy.net (Requires Flash)	20.3-23.5 Mbps
www.speedtest.net	23.3-25.4 Mbps
Appplications/utilities/Speedtest.app
testmy.net [Click "Download Speed Test" then "SmarTest"]	8.0-8.6 Mbps
XFINITY Speed Test
Speed Test - Internet Customer Service | Verizon
Optimum | Speedtest

18 MB png | 129 MB mp4

See Cable Modem Troubleshooting Tips: Speed Tests
Mac - Option click menu bar icon for your Airport to get extended information under the network name. (See network speed in Mac OS X | www.howtogeek.com)

My Network Tests
Oct 2017  Router in Kitchen
Optimum 60 - 79.6, 78.3, 78.9
FIOS 50 - 55.7 , 57.6

FIOS w/ D-Link DIR 868L (AC1750)
Where  RSSI    Tx      Throughput
FR    -67-70  176-234  57.8, 57.9 Mbps
MBR   -73-74   117-176  57.9

ASUS RT-AC1200 
Kit -47 702-867 58Mbps
MBR 2.4GHz -65 117-145  37.7 Mbps
   5GHz -76  117  58.2 Mbps
   
FR -72 117-234 57.8 Mbps

Far side of basement
-64-73  78-130  18 Mbps

5GHz was faster in both places


*RSSI: The 'Received Signal Strength Indication'
      shows the strength of your signal. Closer to 0 is better.
Rate - Transmission Rate modem to MacBook
Throughput  SpeedTest thru Internet
_______________________________ 
2015
Cablevision/Optimum w/ boost (to 50 Mbps) 1/2015 Router in Study
D-Link DIR-868L AC1750
    RSSI*  Rate Throughput
FR -69-76 39-59  58 Mbps  (Family Room)
DR -48    876    60
____________________________
FIOS Jan 2015 20 Mbps Router in Study
Actiontech MI424WR  802.11g
    RSSI*  Rate Throughput
FR -74-76 24-36  12 Mbps  (Family Room)
DR -51    48-54  24
_______________________________


FIOS 9.8/1.8 Mbps Jan 2010
FIOS 24.5 Sat Dec 2012
Cablevision/Optimum with boost (to 30 Mbps)
Wired (20.8-25.4) vs wirless thru 2 walls (21.8-23.8) about the same
Safari and Firefox about the same
Mar 2011 Cablevision/Optimum
4:30 AM  20.8-25.4
10 AM 15.7-22.0
8 PM 19.2-20.0 Mbs
Verizon Samsung Galaxy tab 7 3G
  6 AM  1.2 Mbs; 1.4 Mbs by window
  9:30 AM Sat 0.2, 0.12; 0.24 by window
        subsequent tests didn't work, web response very slow or timeout.
 Verizon FIOS at the Martinsville Rescue Squad:
   5 PM Sat  13 Mbs (same at 6 PM)

Info
DSLReports.com/ ranking of ISPs
reviews-zdnet.com.com/Broadband_Watch/

Bandwidth Speed Test Site List

Note: My tests showed results varied by which test service you used (20%), the media (fiber vs coax [I didn't test DSL]) (50% for some test services), depending on what computer you used (800 MHz PC vs 1GHz Mac) 60%, time of day (3-5%), and which browser you used.
e.g. IE produced the same results except for use with TestMy.net on a Mac where it was 70% slower.

Note: Speakeasy consistently found my Optimum Online (cable) download speed about 20% faster than Verizon FiOS (fiber), while Broadstar and TestMy.net found it about 15% slower. Both were around 10 Mbps download.
On the other-hand upload speeds were 20% slower for Optimum Online with Speakeasy while cable and fiber were the same for Broadstar and TestMy.net; about 1.7 Mbps.

Above tests were done on a Macintosh with OS X 10.4 and a 1 GHz G4 powerbook.
Tests done on a PC with a fresh copy of Windows 2000 on a Dell 800 MHz Pentium III produced speeds 60% slower except for SpeakEasy over verizon fiber which had speed similar to those on the Mac. SpeakEasy over cable service showed speeds 50% slower on the Dell than on the Mac.

The browser used Internet Explorer (IE), Firefox or Safari (Mac) didn't make any difference except for IE on a Mac with TestMy.net where it was 70% slower.

at&t - SBCglobal.net/dsl/speedtest/ Select location in CA, TX, IL, NY, WA, VA
      (upload & download speeds)

at&t/SBC gave results between speakeasy and test my.net on cable (10 Mbps) and very low results (1-2 Mbps) on Verizon fiber.

Browser Performance: Browser Cable fiber Mac PC Mac PC IE Firefox Safari See Also:
Network Performance
ISPs under Data Communications Interfaces