You've heard of "Pocket MSN" (it comes with WM5), now theres
Yahoo Go Mobile for WM3/5 !!
http://go.connect.yahoo.com/go/mobile
Just about everything that we've come to enjoy with Pocket MSN can be done with Yahoo Go Mobile. (no IM client for PPC)
I downloaded the .cab file using Opera, clicked on it and it began installing.
I'm going to assume that the software installs in Main memory by default, as there was NO OPTION presented to choose where the software was installed. Personally, I install EVERYTHING to a SD card and all that ought to get installed on the PPC is a link to the .exe file. (I've read somewhere where .CAB files can be hacked to force installation options, I'm going to look into this)
After installing, a singular Yahoo icon could be found in the Programs directory.
There are a number of unique options here. There are 'filters' for what Yahoo downloads to your handheld. I like the idea of only downloading the last 3 days of email (save memory and time downloading). There are also options to sync with Yahoo photos and Yahoo contacts. (I'll have to investigate the latter one more closely. Did it add all my yahoo contacts to my PPC address book? Which will get synced with my Outlook(s) ??)
So instead of pointing PIE to wap.mobile.yahoo.com, we get a handfull of Yahoo services right on our PPC, just consider it a "Pocket Yahoo" for your PPC.
Enjoy!