Apples 'Mac App Store' is quickly becoming the standard way to get software on the Mac.
However its controlled tightly by Apple and things like Java software are banned on it.
Seems like there's a new serious contender on the platform, the "Mac Download Store" by Amazon.
They already have some good exclusive software and you can sell Java apps and games on it.
You can buy software directly from the Amazon website for both windows and mac, so it could end up becoming like a mini Steam for apps (and games too).
http://arstechnica.com/apple/news/2011/05/amazon-takes-on-mac-app-store-with-mac-downloads-store.arshttp://www.macworld.com/article/160114/2011/05/amazon_mac_software_downloads.html