RadDatePicker

You can add the following code to highlight today's date in the RadDatePicker

 telerik:RadDatePicker ID="dtpDocStart" Culture="en-GB" Width="100px" runat="server" CssClass="RadInput_Default" SharedCalendarID="sharedCalendar">
            Calendar runat="server" UseRowHeadersAsSelectors="False" UseColumnHeadersAsSelectors="False" ViewSelectorText="x">
               SpecialDays>
                  telerik:RadCalendarDay Repeatable="Today" >
                     ItemStyle BackColor="Pink" />
                  /telerik:RadCalendarDay>                
               /SpecialDays>
            /Calendar>
            DatePopupButton ImageUrl="" HoverImageUrl="">/DatePopupButton>
/telerik:RadDatePicker>

 Since you are using shared calendar, you have to configure the calendar control in order to take the changes in effect.

 telerik:RadDatePicker ID="dtpDocStart" Culture="en-GB" SharedCalendarID="sharedCalendar"
        Width="100px" runat="server" CssClass="RadInput_Default">
        Calendar UseRowHeadersAsSelectors="False" UseColumnHeadersAsSelectors="False" ViewSelectorText="x">
        /Calendar>
    /telerik:RadDatePicker>

    telerik:RadCalendar ID="sharedCalendar" runat="server" EnableMultiSelect="false" RangeMinDate="2006/01/01">
        SpecialDays>
            telerik:RadCalendarDay Repeatable="Today">
                ItemStyle BackColor="Pink" />
            /telerik:RadCalendarDay>
        /SpecialDays>
    /telerik:RadCalendar>