Caching in WebParts

Scenario:
You want to use caching in webpart

Solution:
Webpart is just like any other WebControl and can use caching object.

Code:

using System; 
using System.Collections.Generic; 
using System.Text; 
using System.Web.UI; 
using Microsoft.SharePoint; 
using System.Web; 

namespace TrainingSamples { 

public class SimpleCache: System.Web.UI.WebControls.WebParts.WebPart {

protected override void Render (System.Web.UI.HtmlTextWriter writer) { 

base.Render (writer); 

List<SPList> lists = new List<SPList>(); 
string status = ""; 

if (HttpRuntime.Cache["SimpleSampleCache"] == null) 
{ 
status = "The following items are NOT <strong> </ strong> fetched from the cache <br/>"; 

SPWeb web = SPContext.Current.Web; 
foreach(SPList list in web.Lists) 
{
lists.Add (list); 
}

HttpRuntime.Cache.Add( "SimpleSampleCache" lists, null DateTime.MaxValue, TimeSpan.FromMinutes(10), System.Web.Caching.CacheItemPriority.Default, null); 
} 
   else 
   { 
    status = "The following items ARE <strong> </ strong> fetched from the cache! <br/>"; 
    list = (List<SPList>) HttpRuntime.Cache["SimpleSampleCache"]; 
   } 

    writer.Write (status); 

    foreach (l in SPList lists) 
     {
        writer.WriteLine (l.Title + "-" + + l.ItemCount "items <br/>"); 
     }
  } 
 ) 
)

Note:
Another best practice is consider loading the data from SharePoint objects into a DataSet or DataTable if caching is required.
Article:
http://blogs.msdn.com/modonovan/archive/2005/04/27/412505.aspx