Prova così:
<script type="text/javascript">
function setLink(sender) {
var selVal = $('#radioList input:checked').val();
sender.href = 'http://www.google.it?param=' + selVal;
}
</script>
<div>
<asp:RadioButtonList runat="server" ID="radioList">
<asp:ListItem Text="Item 1" Value="0" />
<asp:ListItem Text="Item 2" Value="1" />
<asp:ListItem Text="Item 3" Value="2" />
</asp:RadioButtonList>
</div>
<div>
<asp:HyperLink ID="lnkServer" runat="server" Text="Cliccami (server)" onclick='javascript:setLink(this)' />
<a id='lnkClient' href='#' onclick='javascript:setLink(this)' >Cliccami (client)</a>
</div>