How to create "minus addresses" on Google Apps. It involves creating a catch-all and creating filters that forward the messages to the appropriate account. Clever workaround.
Google's CalDAV api documentation. Their calendar service supports some caldav functionality, but not all. Interesting potential for soundclient.
Very interesting article including good links and background info on how to create an XMPP bot. Virtually no use to me right now, but one to file away... :-)
FuseMail is a hosted mail service which includes webmail, IMAP, POP3, calendar functions, shared files, groupware, and more. All for $2/month/mailbox. Great.
Thinkfree is similar to Zoho. It's a hosted, online office suite. It's also available in self installed versions. No email capability (that I can see).
Google Apps is the hosted mail / docs / etc product from Google. It comes in Free or Premier ($50/year/user).
Zoho is an online office suite, similar to Google Apps. It includes a hosted mail product.
Zimbra is an open source email / collaboration software. They offer a hosted service starting from $400/year for 15 pro mailboxes.