JPerf!

iperf is a tool for active measurements of the maximum achievable bandwidth on IP networks. It supports tuning of various parameters related to timing, protocols, and buffers. For each test it reports the bandwidth, loss, and other parameters.

PPerf - PowerShell Iperf GUI

IxChariot is the industrys leading test tool for simulating real-world applications to predict device and system performance under realistic load conditions. Comprised of the IxChariot Console, Performance Endpoints and IxProfile, the IxChariot product family offers thorough network performance assessment and device testing by simulating hundreds of protocols across thousands of network endpoints. IxChariot provides the ability to confidently assess the performance characteristics of any application running on wired and wireless networks »

NetStress includes the following features:

Qcheck, the network troubleshooting utility from Ixia, quickly checks network response time, throughput, and streaming performance. It even runs anywhere-to-anywhere traceroute!

Javascript performance benchmark playground based on Benchmark.js. You can write, run, share and fork JavaScript tests online.

LANBench is a simple LAN / TCP Network benchmark utility. It is designed for testing network performance between two computers and is based on Winsock 2.2. LANBench tests TCP performance only and is designed for minimal CPU usage so that the pure performance of your network could be fully tested.

GL's PacketCheck™- is a PC based Ethernet test tool that is designed to check frame transport ability, and throughput parameters of Ethernet and IP networks

Ping like tool that relies on the common ICMP echo mechanism to determine the bandwidth between your computer and a remote host.

A utility for testing the performance of a wireless or wired network that sends TCP and UDP data streams and computes important metrics: upstream and downstream throughput values, packet loss, and round-trip time, etc. It supports both IPv4 and IPv6 connections.