Google Talk’s voicemail feature allows your friends and contacts to send a voice message to your Gmail account. Voicemails show up as special messages in your Inbox, just click the Play button in the conversation view and Gmail’s built in Flash player automatically plays them for you.
Voicemails can be searched in your Gmail account using is:voicemail
Another feature I noticed is that if your contacts send you offline messages from Google Talk, these messages are delivered to your GMail Inbox as emails with the subject “Chat with XXX” and can be viewed as conversations.
I wonder why Yahoo! and Microsoft cannot tightly integrate their webmail and IM features as Google does it so beautifully.