Four cool things to write about, two from Google and two from Yahoo:
Google Earth: A free and improved version of Keyhole, a cool satellite mapping system that until now was available only by subscription (the service still sell premium subscriptions). Basically, this is an interactive mapping service that uses satellite imagery and 3-D perspective in a really cool way. If you've ever wanted to see what it would look like to fall to Earth from space, here's your chance. Recent improvements include 3-D terrain and buildings for major cities (rather than a perspective view of 2-D pictures) and fly-through driving directions, which actually might come in handy.
Personalized Google search: Now Google can (optionally) keep track of your searches to get a better idea of what you're looking for in future searches. I haven't actually seen the filter in action yet -- Google says it may take awhile to get a good search history. The results page will indicate whether the search has been personalized, for times when you want a standard search. And you can always turn off the feature permanently.
Yahoo Music Unlimited: I don't quite like the standalone player, but $7 per month, a nice selection of tunes and and 192-kbps encoding add up to the best subscription music service on the market. Yahoo has published the players APIs, which could lead to all sorts of cool add-ons. Someone has already created a taskbar mode that works a lot like the one for Windows Media Player. I hope this isn't a bug, but I can transfer protected files just fine to my iPaq, even though it's not listed as a compatible device.
Yahoo mail: I haven't seen the actual beta yet, but the company has announced a faster, easier-to-use e-mail service that makes better use of Web scripting and XML (for you techies, a set of technologies collective known as AJAX -- Asynchronous JavaScript and XML). If you use Google's Gmail or Google Maps, you already know why this is a big deal. Yahoo bought Web e-mail firm Oddpost last year, but this is the first confirmation they'll be using the technology for its free e-mail service. I still pay for Yahoo Mail Plus because of the excellent spam filter, disposable addresses and because it serves as my "permanent" address.