Use People Picker in custom web part

Try the following

Include the Tagprefix at the top in your webpart ascx file where there are all the tag prefixes.

Then include the PeopleEditor wherever you want.

<%@ Register Tagprefix="SharePoint" Namespace="Microsoft.SharePoint.WebControls" Assembly="Microsoft.SharePoint, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>

<SharePoint:PeopleEditor ID="spPeoplePicker" runat="server" Width="350" SelectionSet="User" />

Insert something like this in code behind

if (spPeoplePicker.ResolvedEntities.Count > 0)

                    {

                        PickerEntity selectedEntity = (PickerEntity)spPeoplePicker.ResolvedEntities[0];

UserProfile profile= upm.GetUserProfile(selectedEntity.Key);

}

Modify as per your requirement.

Also refer the following link

http://karinebosch.wordpress.com/sharepoint-controls/peopleeditor-control/

Yes, you can populate a dropdown with values from a list field

<asp:DropDownList ID="ddlDropDown" runat="server" >

    </asp:DropDownList>

In the code behind include

SPWeb web = SPContext.Current.Web;

SPList list = web.Lists["ListName"];

                SPListItemCollection items= list.GetItems();

                if (items!= null)

                {

                   

                    foreach (SPListItem item in items)

                    {

                        if (item["FieldName"] != null)

                            ddlDropDown.Items.Add(item["FieldName"].ToString());

                    }

                }