Beginning this month, we're doing a new series of posts where we quickly feature five great free apps across all categories that we think your Windows Phone should have. So here are this month's picks:

1. Adobe Reader

   Adobe Reader is an absolutely essential application for a true smartphone experience. It allows you to open PDF documents in email attachments, on the Web, or from the phone.

   

   Download

2. WP Bench

   WP Bench is a performance benchmarking application for Windows Phone devices. It tests your CPU, GPU, memory, storage, display and battery, and lets you publish your score to the online charts to compare with other users. It's the first benchmarking app for WP7.

   

   Download

3. Wunderlist

   Wunderlist is a very popular multi-platform task manager and to-do app, and is now available for Windows Phone. It comes with free cloud sync.

   

   Download

4. Skype

   Just like its desktop counterpart, you can make and receive voice/video calls and instant messages for free from anyone using Skype, or call and text any phone number with Skype Credit.

   

   Download

5. Contact Sender

   If you've ever gotten into a situation where you have to share details of a contact with someone, you know it's very time-consuming. Contact Sender finishes the task in seconds. Just select the details and send it via SMS or email.

   

   Download

Discover more great free apps for Windows Phone.

Image credit: Windows Phone Marketplace (modified)