Yesterday while adding support for multi-cultural stylesheets to one of the sites I'm currently working on, 
I decided to rethink the way I usually implement this very common task. Until yesterday, I will have two literals 
hosting the links tags each one pointing to a different stylesheet file, on my code behind I will check the current culture 
and show the literal hosting the proper stylesheet link.
 
Well, that was, until yesterday, because I decided I wanted to create an easier way to accomplish this and not to settle 
for the not-so-elegant but convenient copy-and-paste :-)
 
After searching for possible solutions already available I found this article on weblogs.asp.net and I used it as start point 
for my control.
 
This is the custom control I finally came with:
 
[DefaultProperty("Text")]
[ToolboxData("<{0}:LinkExtended runat=server>")]
public class LinkExtended : System.Web.UI.WebControls.WebControl
{
   #region Constants
   private const string CULTURE_DEFAULT = "en-CA";
   #endregion
 
   #region Fields
   protected bool isDesignMode = false;
   protected string linkUrl = "";
   protected string linkType = "";
   protected string linkRelationship = "";
   protected string defaultCulture = CULTURE_DEFAULT;
   protected bool useUICulture = true;
   #endregion
 
   #region Constructor
   public LinkExtended() : base()
   {
      this.isDesignMode = (System.ComponentModel.LicenseManager.UsageMode == 
                           System.ComponentModel.LicenseUsageMode.Designtime);
   }
   #endregion
 
   #region Protected Methods
   protected override void Render(HtmlTextWriter writer)
   {
      // Retrieve current culture
      string cultureName = this.DefaultCulture;
      
      if (!this.isDesignMode && this.UseUICulture)
         cultureName = Thread.CurrentThread.CurrentUICulture.Name;
 
      // parse link url
      this.LinkUrl = this.LinkUrl.Replace("{culture}", cultureName);
 
      // Render control
      writer.WriteBeginTag("link");
      writer.WriteAttribute("type",this.LinkType);
      writer.WriteAttribute("rel",this.LinkRelationship);
      writer.WriteAttribute("href",base.ResolveUrl(this.LinkUrl));
      foreach (string key in this.Attributes.Keys)
      {
         writer.WriteAttribute(key,this.Attributes[key]);
      }
      writer.Write(HtmlTextWriter.TagRightChar);
      writer.WriteEndTag("link");
   }
 
   protected override object SaveViewState() 
   { 
      object[] newstate = new object[5];
      newstate[0] = (object)this.linkType; 
      newstate[1] = (object)this.linkRelationship; 
      newstate[2] = (object)this.linkUrl; 
      newstate[3] = (object)this.defaultCulture; 
      newstate[4] = (object)this.useUICulture; 
      return newstate;
   }
 
   protected override void LoadViewState(object savedState)
   {
      object[] newstate = (object[])savedState;
      this.linkType = (string)newstate[0];
      this.linkRelationship = (string)newstate[1];
      this.linkUrl = (string)newstate[2];
      this.defaultCulture = (string)newstate[3];
      this.useUICulture = (bool)newstate[4];
   }
   #endregion
 
   #region Propeties
   [DefaultValue("")]
   [Category("Appearance")]
   [Description("The type html attribute.")]
   [Bindable(true)]
   public virtual string LinkType
   {
      get {return linkType;}
      set {linkType = value;}
   }
 
   [DefaultValue("")]
   [Category("Appearance")]
   [Description("The rel html attribute.")]
   [Bindable(true)]
   public virtual string LinkRelationship
   {
      get {return linkRelationship;}
      set {linkRelationship = value;}
   }
 
   [DefaultValue("")]
   [Category("Appearance")]
   [Description("The href html attribute.")]
   [Bindable(true)]
   public virtual string LinkUrl
   {
      get {return linkUrl;}
      set {linkUrl = value;}
   }
 
   [DefaultValue(CULTURE_DEFAULT)]
   [Category("Appearance")]
   [Description("The default culture.")]
   [Bindable(true)]
   public virtual string DefaultCulture
   {
      get {return defaultCulture;}
      set {defaultCulture=value;}
   }
 
   [DefaultValue(true)]
   [Category("Appearance")]
   [Description("If true the current UI Culture will be used at runtime.")]
   [Bindable(true)]
   public virtual bool UseUICulture
   {
      get {return useUICulture;}
      set {useUICulture = value;}
   }
   #endregion
}
 
 
And then, just by adding the following line to my pages I get the desired functionality:
 
 
Hope this helps... :-)