How big is the environment? If it is under 3000 IPs then you can look at something like GFI LANguard, this does vulnerability scanning with patch management. Supports multi-platform and 3rd party applications I believe (from last time I worked with it). Another option is Dell Kace appliance. I've worked with this as well. This supports Mac, Linux and Windows. along with support for 3rd parties, you can create custom install scripts for apps that may not be in their library. Similar to using GPO but I found it to be much cleaner, and again, it supports multiple platforms. I think they are even moving into mobile support for iPads and other types of tablet devices. It works as a decent inventory tool as well.