Popular Apks Downloader.
Also, the apps you want to download can be specified in a json file and it will download them to the appropriate folders.
You can use the script : https://github.com/Machiry/Android/blob/master/HelperScripts/GetFreeAppsListFromAppGravity.py to generate the json file. The above script scraps appsgravity.org to get the list of free package names and the appropriate categories.
To Run the script you need BeautifulSoup library to be present. You can get it from: http://www.crummy.com/software/BeautifulSoup/
To Download Apps from http://slideme.org/:
Like google play, slideme.org is a market place hosting android apps. The script: https://github.com/Machiry/Android/blob/master/HelperScripts/DownloadFreeApksFromSlideMe.py can be used to download all the free apps from it.
Again as mentioned before : To Run the script you need BeautifulSoup library to be present. You can get it from: http://www.crummy.com/software/BeautifulSoup/