Something

<form method="post" action="send_msg.php">
	<table border="0"  cellspacing="0" cellpadding="0" align="center" width="450">
		<tr width="250" align="center">
			<td>Subject</td>
			<td><input type="text" name="subject" /></td>
		</tr>

		<tr bgcolor="#f1f1f1" width="250" align="center">
			<td>Send to</td>
			<td><input type="text" name="mailto" value="<?php echo $email ?>" /></td>
		</tr>
		<br />
		<tr>
			<td colspan="2" align="center"><textarea cols="35" rows="8" name="message"></textarea></td>
		</tr>
		<br />
		<tr>
			<td><input type="submit" value="Send message" /></td>
		</tr>
	</table>
</form>

$mailto = $_POST["mailto"];
$message = $_POST["message"];
$subject = $_POST["subject"];
$myemail = "greg@gottschalkknives.com";

mail($mailto, $subject, $message, "From: $myemail\r\nReply-to: $myemail\r\n");