Google's Go Programming Language: 30 Ways to Make It Better
GG: A Build Tool for Go in Go Tool
GG is a builder for the Go language. It makes it easy to build your Go files into an executable file. It's released under the terms of the BSD License. GG is not as powerful as make utility. But it lets you build a simple file or a simple project. Projects can be described in the YAML language.

GVM, or Go Version Manager
GVM provides an interface to manage Go versions.

Gocheck: Rich Test Framework With Suites, Fixtures, Assertions, Etc.
The Go language provides an internal testing library, named testing, which is relatively slim due to the fact that the standard library correctness by itself is verified using it. The Gocheck package, on the other hand, expects the standard library from Go to be working correctly, and builds on it to offer a richer testing framework for libraries and applications to use.

Chimp
Chimp is a library to provide the Go language with automation tools. It can be used to write build scripts, deploy scripts, etc.

Gomemcached
A memcached server in Go.

Go-Options
A command line parsing library for Go.

GoPasswordCreator
A small tool that creates random passwords

Oh
A Unix shell written in Go.

GOOP
Dynamic object-oriented programming support for Go: https://github.com/losalamos/goop

DBGo
A lightweight relational flat-file database engine for Go: https://github.com/HouzuoGuo/DBGo

GoMySQL
MySQL library for Go: https://github.com/Philio/GoMySQL

MyMySQL
MySQL Client API written entirely in Go: https://github.com/ziutek/mymysql

Couch-Go
A newer maintained CouchDB database binding: http://code.google.com/p/couch-go/

Go-DB
A generic database API: https://github.com/phf/go-db

Go Database Interface
Here is a Go interface to Oracle Database: https://github.com/garyburd/go-mongo

Working with Go and MongoDB
This is a driver for MongoDB: https://github.com/garyburd/go-mongo

Working with Go and MySQL
This is a MySQL wrapper for Go: https://github.com/yone098/go-mysql

Creating Go Projects
Here is a tool to create new Go projects: https://github.com/bmatsuo/gonew

Running Go Scripts
This is a tool to run Go scripts: https://github.com/kless/gonow

Go Cloud Backup Utilities
The projects feature small Go utilities to back up data from the cloud to the cloud: https://github.com/nictuku/Cloud-Backups

Eclipse IDE for Go
GoClipse is an Eclipse plug-in that adds integrated development environment (IDE) functionality to the Eclipse platform for the Go programming language. The purpose of GoClipse is to create an environment in which the development of Go is easy for a beginner to an intermediate user: http://code.google.com/p/goclipse/

Go Interpreter
Interpreted Go implementation for Windows: http://www.unicorn-enterprises.com/express_go.html

Experimental Go Compiler
This is an experimental source-to-source compiler for Go: https://github.com/droundy/go-crazy

Go Project Creation Wizard
Tool to create skeleton of Go projects: https://github.com/kless/gowizard

JavaScript Engine Wrapper for Go
This is a wrapper for WebKit's JavaScript engine for Go: https://bitbucket.org/rj/javascriptcore-go/overview

Flash Player for Go
Here is a Flash player implementation in Go language: http://sourceforge.net/p/goflash/home/Home/

Twitter Command Line
This is a simple Twitter command line client: https://github.com/jb55/go-twitter

Google App Engine Connection
Here is a Web framework for Google App Engine Link: https://github.com/georgenava/appgo

Gorilla Web Toolkit for Go
This is the Gorilla Web toolkit for the Go programming language: http://code.google.com/p/gorilla/

Application Framework for Go
Go-webproject is an open-source Web application framework written in the Go Programming Language: http://go-webproject.appspot.com/

