Samples showing how to download nuget in a scrpit to avoid checking it in

getnuget.proj

<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003" DefaultTargets="GetNuget">

  <!--
  This is an MSBuild snippet that can be used to download nuget to the path
  in the property NuGetExePath property.
  
  Usage:
   1. Copy and paste this into your build script
   2. Call the GetNuGet target before you use nuget.exe from $(NuGetExePath)
  -->
  
  <PropertyGroup>
    <NuGetExePath Condition=" '$(NuGetExePath)'=='' ">$(localappdata)\LigerShark\AzureJobs\tools\nuget.exe</NuGetExePath>
    <NuGetDownloadUrl Condition=" '$(NuGetDownloadUrl)'=='' ">http://nuget.org/nuget.exe</NuGetDownloadUrl>
  </PropertyGroup>
  
  <Target Name="GetNuget" Condition="!Exists('$(NuGetExePath)')">
    <Message Text="Downloading nuget from [$(NuGetDownloadUrl)] to [$(NuGetExePath)]" Importance="high"/>
    <ItemGroup>
      <_nugetexeitem Include="$(NuGetExePath)" />
    </ItemGroup>
    <MakeDir Directories="@(_nugetexeitem->'%(RootDir)%(Directory)')"/>
    <DownloadFile
        Address="$(NuGetDownloadUrl)"
        FileName="$(NuGetExePath)" />    
  </Target>

  <PropertyGroup Condition=" '$(ls-msbuildtasks-path)'=='' ">
    <ls-msbuildtasks-path>$(MSBuildToolsPath)\Microsoft.Build.Tasks.v4.0.dll</ls-msbuildtasks-path>
    <ls-msbuildtasks-path Condition=" !Exists('$(ls-msbuildtasks-path)')">$(MSBuildFrameworkToolsPath)\Microsoft.Build.Tasks.v4.0.dll</ls-msbuildtasks-path>
    <ls-msbuildtasks-path Condition=" !Exists('$(ls-msbuildtasks-path)')">$(windir)\Microsoft.NET\Framework\v4.0.30319\Microsoft.Build.Tasks.v4.0.dll</ls-msbuildtasks-path>
  </PropertyGroup>
  
  <UsingTask TaskName="DownloadFile" TaskFactory="CodeTaskFactory" AssemblyFile="$(ls-msbuildtasks-path)">
    <!-- http://stackoverflow.com/a/12739168/105999 -->
    <ParameterGroup>
      <Address ParameterType="System.String" Required="true"/>
      <FileName ParameterType="System.String" Required="true" />
    </ParameterGroup>
    <Task>
      <Reference Include="System" />
      <Code Type="Fragment" Language="cs">
        <![CDATA[
            new System.Net.WebClient().DownloadFile(Address, FileName);
        ]]>
      </Code>
    </Task>
  </UsingTask>
  
</Project>

getnuget.ps1

<#
.SYNOPSIS
    You can use this to get the path of nuget.exe. If nuget.exe is not in
    the $toolsDir specfied it will be downloaded from $nugetDownloadUrl.

    To use this in your script just copy/paste the Get-NuGet function below
    and then call Get-NuGet to return the path to the .exe. It will take care
    of downloading it if it's missing.
#>
[cmdletbinding()]
param(
    $toolsDir = ("$env:LOCALAPPDATA\LigerShark\AzureJobs\tools\"),
    $nugetDownloadUrl = 'http://nuget.org/nuget.exe'
)

<#
.SYNOPSIS
    If nuget is not in the tools
    folder then it will be downloaded there.
#>
function Get-Nuget{
    [cmdletbinding()]
    param(
        $toolsDir = ("$env:LOCALAPPDATA\LigerShark\tools\"),
        $nugetDownloadUrl = 'http://nuget.org/nuget.exe'
    )
    process{
        if(!(Test-Path $toolsDir)){
            New-Item -Path $toolsDir -ItemType Directory -Force | Out-Null
        }

        $nugetDestPath = Join-Path -Path $toolsDir -ChildPath nuget.exe
        
        if(!(Test-Path $nugetDestPath)){
            'Downloading nuget.exe' | Write-Verbose
            (New-Object System.Net.WebClient).DownloadFile($nugetDownloadUrl, $nugetDestPath)

            # double check that is was written to disk
            if(!(Test-Path $nugetDestPath)){
                throw 'unable to download nuget'
            }
        }

        # return the path of the file
        $nugetDestPath
    }
}

Get-Nuget -toolsDir $toolsDir -nugetDownloadUrl $nugetDownloadUrl