procedure TForm1.Button1Click(Sender: TObject);
var
  Http  : TidHttp;
  CM    : TidCookieManager;
  Data  : TStringList;
  StrPage, UserID,  UserName  :  String;
  i : integer;
begin
  try
    Http := TIdHTTP.Create(Self);
    Data := TStringList.Create;
    CM := TidCookieManager.Create(Http);
    Http.AllowCookies := true;
    Http.CookieManager := CM;
    Http.HandleRedirects := true;

    Http.Request.Host:='login.vk.com';
    Http.Request.UserAgent:='Mozilla/5.0 (Windows; U; Windows NT 5.1; ru; rv:1.9.0.10) Gecko/2009042316 Firefox/3.0.10';
    Http.Request.Accept:='text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8';
    Http.Request.AcceptLanguage:='ru,en-us;q=0.7,en;q=0.3';
    Http.Request.AcceptCharSet:='windows-1251,utf-8;q=0.7,*;q=0.7';
    Http.Request.Referer:='http://vkontakte.ru/';

    Data.Add('login=login');
    Data.Add('email=' + Edit1.Text);
    Data.Add('pass=' + Edit2.Text);
    StrPage := Http.Post('http://login.vk.com/?act=login', Data);
  finally
    Data.Free;
    CM.Free;
    Http.Free;
  end;

  if Pos('<title>В Контакте | Вход</title>',StrPage) <> 0 then
    ShowMessage('Авторизация провалилась')
  else
    ShowMessage('Авторизация прошла успешно');

  Memo1.Lines.Text := StrPage;
end;

<title>В Контакте | Вход</title>

>Такой почтовый адрес не зарегистрирован, либо пароль неверный.</div>

http://vkontakte.ru/login.php

POST /login.php HTTP/1.1
Host: vkontakte.ru
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; ru; rv:1.9.1.5) Gecko/20091102 MRA 5.4 (build 02647) Firefox/3.5.5 WebMoney Advisor
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: ru,en-us;q=0.7,en;q=0.3
Accept-Encoding: gzip,deflate
Accept-Charset: windows-1251,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
X-Requested-With: XMLHttpRequest
Referer: http://vkontakte.ru/
Content-Length: 18
Cookie: remixlang=0; remixchk=5; remixautobookmark=30; remixclosed_tabs=0; remixgroup_closed_tabs=0; remixfilters=8191; remixdeffriendgroups=164; remixnews_privacy_filter=0; remixnews_types=2147478270; remixclosed_tabs=6; remixref=1; remixnews_privacy_filter=0; remixgroup_closed_tabs=0; audio_vol=80; remixsid=nonenone
Pragma: no-cache
Cache-Control: no-cache
op=a_login_attempt


HTTP/1.x 200 OK
Server: nginx/0.7.59
Date: Wed, 25 Nov 2009 10:30:11 GMT
Content-Type: text/html; charset=windows-1251
Connection: keep-alive
X-Powered-By: PHP/5.2.6-1+lenny3
Pragma: no-cache
Cache-Control: no-store
Vary: Accept-Encoding
Content-Length: 7
----------------------------------------------------------
http://login.vk.com/?act=login

POST /?act=login HTTP/1.1
Host: login.vk.com
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; ru; rv:1.9.1.5) Gecko/20091102 MRA 5.4 (build 02647) Firefox/3.5.5 WebMoney Advisor
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: ru,en-us;q=0.7,en;q=0.3
Accept-Encoding: gzip,deflate
Accept-Charset: windows-1251,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
Referer: http://vkontakte.ru/
Cookie: remixlang=0; remixchk=5; remixsid=d0295
Content-Type: application/x-www-form-urlencoded
Content-Length: 62
email=lol%40mail.ru&pass=715&expire=&vk=


HTTP/1.x 200 OK
Server: nginx/0.7.59
Date: Wed, 25 Nov 2009 10:30:11 GMT
Content-Type: text/html; charset=windows-1251
Connection: keep-alive
X-Powered-By: PHP/5.2.6-1+lenny3
Pragma: no-cache
Cache-Control: no-store
P3P: CP="IDC DSP COR ADM DEVi TAIi PSA PSD IVAi IVDi CONi HIS OUR IND CNT"
Set-Cookie: l=13262199; expires=Sat, 20-Nov-2010 22:45:10 GMT; path=/; domain=login.vk.com
Set-Cookie: p=73bf60d54f67; expires=Sat, 27-Nov-2010 17:03:12 GMT; path=/; domain=login.vk.com
Content-Encoding: gzip
Vary: Accept-Encoding
Content-Length: 339