RedditBar
Quickly open Reddit links and get notified about new PMs, right from your Mac system menu bar.
Requires Mac OS X 10.8 or newer
Full control
View links from your Frontpage or only show specific subreddits. You can also specify how many links you want to see at once.
Orangered
Get notified about new PMs or replies to your posts and comments. The refresh interval is configurable!