Here are some utils methods to compress/decompress byte data in gzip format. Couldn't really find many examples to inflate (decompress) the byte data after it's been compressed...maybe i just didn't Google hard enought 
. Pretty cool library...especaily when you reduce a bitmap 80-90%!!
Note: This is only a wrapper to the main SharpZipLib library available at http://www.icsharpcode.net/OpenSource/SharpZipLib/Default.aspx so you will need that library for the utils to work.
/// <summary>
/// Compress the raw data using gzip compression
/// </summary>
/// <param name="rawData"></param>
/// <returns></returns>
public static byte[] DeflateData(byte[] data)
{
MemoryStream stream = new MemoryStream();
GZipOutputStream gzipOut = new GZipOutputStream(stream);
gzipOut.Write(data,0,data.Length);
gzipOut.Finish();
return stream.ToArray();
}
/// <summary>
/// Decompress the data using gzip compression
/// </summary>
/// <param name="data"></param>
/// <returns></returns>
public static byte[] InflateData(byte[] data)
{
MemoryStream ms = new MemoryStream();
ms.Write(data,0,data.Length);
ms.Seek(0,SeekOrigin.Begin);
Stream gzin = new GZipInputStream(ms);
MemoryStream decompMemStream = new MemoryStream();
int size = 2048;
byte[] buffer = new byte[size];
while(size>0)
{
size = gzin.Read(buffer, 0, size);
if (size > 0)
decompMemStream.Write(buffer, 0, size);
}
return decompMemStream.ToArray();
}