Without going through Google Calendar? I'm not aware of any. Jorte, which arguably the best of the free calendar apps, requires the Outlook calendar be synced to the Google Calendar so it can pull in the data.
I dont know how you guys do it, but I have done it with the native calendar app on my phone and tablet.
1. I don't sync my Outlook with Google calendar. I tried that once and got duplicates of everything.
2. Start the native app, go to tools, add account. There should be an option for "Corporate". Add the corporate account and set it up.
3. There will now be two accounts, the Google account and the "Corporate/Outlook" account.
4. You must select the "Corporate/Outlook" account as default.
The corporate accounts though require knowledge of the domain and username to properly work. The OP hasn't specified whether or not he is using Outlook for corporate or personal purposes, which does make a difference. If the OP is using Outlook for personal purposes he isn't going to have the domain and username. That pretty much leaves him with syncing with Google.