Is there any enterprise distribution program for blackberry applications?
Is there any method similar to Apple's enterprise distribution of iphone applications?
While going through their documentation, they are talking about using a deployment server and distributing apps with it.
Note: for early OS versions of blackberry - OS 7 or previous versions are my target
As Peter said in his answer, you can use BES to distribute applications in an Enterprise environment.
In iOS, the Enterprise program is basically the only Apple-approved way to deploy software, other than via the iTunes App Store (ignoring how you deploy to your test team).
BlackBerry Java (e.g. OS 5,6,7) devices don't have the same restriction on apps that Apple has implemented. Normal jailed iPhones cannot install software from any arbitrary web server, but BlackBerry devices can.
So, another option is just to post your app (.jad and .cod files) to a (corporate) webserver, and let users download the apps themselves. This is called Over-The-Air (OTA) deployment.
I'm not endorsing this over BES deployment, just adding to your options.