Interesting alternative to FeedBurner. Private service that charges for feed stuff, email subscriptions, etc. Starts from $1.49 per month for up to 9 subscribers.
Google Apps is the hosted mail / docs / etc product from Google. It comes in Free or Premier ($50/year/user).
Interesting data serialisation format, alternative to json / PHP's serialize, etc. Designed to be fast and small.
Zoho is an online office suite, similar to Google Apps. It includes a hosted mail product.
Handy comparison of online outliners. Useful research info.