Intent intent = new Intent();
ComponentName cmp = new ComponentName("com.sina.weibo","com.sina.weibo.EditActivity");
intent.setAction(Intent.ACTION_MAIN);
intent.addCategory(Intent.CATEGORY_LAUNCHER);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
intent.setComponent(cmp);
startActivityForResult(intent, 0);

新浪微博（编辑界面）：com.sina.weibo           com.sina.weibo.EditActivity

腾讯微博（编辑界面）：com.tencent.WBlog        com.tencent.WBlog.activity.MicroblogInput

微信：                com.tencent.mm           com.tencent.mm.ui.LauncherUI

QQ:                com.tencent.mobileqq     com.tencent.mobileqq.activity.HomeActivity

Intent intent=new Intent(Intent.ACTION_SEND);   

intent.setType("text/plain");   

intent.putExtra(Intent.EXTRA_SUBJECT,"分享");   
intent.putExtra(Intent.EXTRA_TEXT, "hello，weibo！");    
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);   
startActivity(Intent.createChooser(intent, "share"));