The TaskMailer application that is currently available as free demo version has some problems right now. It is compatible with industry standards like ICal and VCal but it seems the most famous desktop task management application Microsoft Outlook does not support this format - at least not for tasks. It is easy to import ICal or VCal meeting / calendar requests into your Outlook calendar but tasks / todos are not recognized.
I just found an application called Sunbird which is made by the Mozilla guys (maker of Thunderbird email client and Firefox browser). This task / calendar management application supports ICal and VCal formats by default. Therefor, you can easily import a task into Sunbird which has been sent from your BlackBerry using TaskMailer to your mailbox.
Here is a Sunbird screen shot:

Sunbird site: http://www.mozilla.org/projects/calendar/sunbird/download.html
Thunderbird Plugin Lightning
If you are using Thunderbird as email client you might want to have a more seamless integration into it. This just makes sense as you get your email into your Thunderbird email client anyway. Lightning is an extension for Thunderbird which provides exactly this.
Here is a Lightning screen shot:

Thunderbird site: http://www.mozilla.com/en-US/thunderbird/
Lightning site: http://www.mozilla.org/projects/calendar/lightning/

