Enter SecondToday.

Here’s how I customised my soft keys to launch SecondToday instead of Phone. I already have a hard key for phone.

1. First install SecondToday
2. Fire up your registry editor and go to “\HKLM\Software\HTC\Manila”
3. Change the value of “HomeLSKPath” to the EXACT location of SecondToday.exe, e.g, “\Programs Files\SecondToday\SecondToday.exe” or “\storage Card\Programs Files\SecondToday\SecondToday.exe”
4. Change the value of “HomeLSKText” to “SecondToday” or whatever text that you want to replace “Phone”
5. Soft reset your phone

6. After soft reset, it should show on the LEFT softkey “SecondToday”
7. Click on the LEFT soft key “SecondToday”, SecondToday will be launched.
8. Select the plugins you will like to be displayed and click ok.
9. Now, you are done. To return to Touch Flo, just click on the Home hard key.

To add Secondtoday to the Exclusive List
1. Go to Task Manager, Tap and HOLD onto SecondToday in the Task Manager
2. Select the option “Add Exclusive” on the popup menu.

Source: http://forum.xda-developers.com/showthread.php?t=401907