[MENTION=1347]fahd[/MENTION]! There are three places to download cracked games/apps for Android.
1. Mobilism (Its a forum, google it)
2. MarketMilitia (Pretty much same thing as Mobilism, although i personally hate the advertisements on the forum)
3. BlackMart (Its like a Blackmarket, get the apk from 4Shared and install on your phone.
Now, you can either download them directly on your Phone, or Download the at your PC and then transfer to your device.
There isn't any risks involved. "Cracked" apps are just what they are supposed to mean, CRACKED.
About MicroSD Card, well you dont really need it for the apps (Apps will always be installed on Internal SD Card anyway, UNLESS you move them to External one. Then there is the problem that you can't really transfer MOST of the apps to the external SD Card).
If you are a big apps junkie then you should get a MicroSD Card, to store all your Music, Photos, and Application Installers and stuff. It'll keep the INTERNAL MEMORY of the phone FREE, so that you'll have MORE memory available for installing apps.