ImageGenFetch - when taking a copy of an Umbraco site from a production server, the /media directory can be a huge download. So if using ImageGen you can auto-download the /media images on-demand.

CheckImageGenModule.cs

using System;
using System.IO;
using System.Net;
using System.Net.Mime;
using System.Text;
using System.Web;

namespace Umbrella.ImageGenFetch
{
	public class CheckImageGenModule : IHttpModule
	{
		public void Dispose() { }

		public void Init(HttpApplication context)
		{
			context.PostRequestHandlerExecute += new EventHandler(context_PostRequestHandlerExecute);
		}

		private void context_PostRequestHandlerExecute(object sender, EventArgs e)
		{
			if (HttpContext.Current == null)
				return;

			var context = HttpContext.Current;
			var request = context.Request;
			var currentExecutionFilePath = request.CurrentExecutionFilePath;

			if (!string.Equals(currentExecutionFilePath, "/ImageGen.ashx", StringComparison.OrdinalIgnoreCase))
				return;

			var response = context.Response;
			if (response.ContentType != MediaTypeNames.Text.Html)
				return;

			var image = request.QueryString["image"];
			if (string.IsNullOrWhiteSpace(image))
				return;

			response.Filter = new FetchRemoteImage(response.Filter, image, context.Server.MapPath(image), "http://www.domain.com");
		}
	}
}

FetchRemoteImage.cs

using System;
using System.IO;
using System.Net;
using System.Net.Mime;
using System.Text;
using System.Web;

namespace Umbrella.ImageGenFetch
{
	public class FetchRemoteImage : MemoryStream
	{
		private string Domain;
		private Stream OutputStream;
		private string LocalPath;
		private string UrlPath;

		public FetchRemoteImage(Stream output, string urlPath, string localPath, string domain)
		{
			this.Domain = domain;
			this.OutputStream = output;
			this.LocalPath = localPath;
			this.UrlPath = urlPath;
		}

		public override void Write(byte[] buffer, int offset, int count)
		{
			var content = UTF8Encoding.UTF8.GetString(buffer);
			if (content.StartsWith("File not found:"))
			{
				var url = string.Concat(this.Domain, this.UrlPath);
				var path = this.LocalPath;

				var directory = Path.GetDirectoryName(path);
				if (!Directory.Exists(directory))
					Directory.CreateDirectory(directory);

				using (var client = new WebClient())
				{
					client.DownloadFile(url, path);
				}

				// TODO: Read the downloaded image, output to buffer
			}

			var outputBuffer = UTF8Encoding.UTF8.GetBytes(content);
			this.OutputStream.Write(outputBuffer, 0, outputBuffer.Length);
		}
	}
}

Web.config

<add name="ImageGenFetch" type="Umbrella.ImageGenFetch.CheckImageGenModule,Umbrella.ImageGenFetch" />