It's all been said and done in other blogs, but for my own readers I'll compress these bits and pieces of information together.
GDrive: Some rumors from Google seem to be set up to be just that: informations is leaked on purpose for people to speculate. This seems to be the case here, as last week's Google Analyst Day yielded a powerpoint presentation that was later removed, but not before being seen by just enough people that it's content was relatively widely known. The powerpoint mentions something about GDrive as being "Infinite storage, where we can house all user files, including: emails, web history, pictures, bookmarks, etc and make it accessible from anywhere (any device, any platform, etc)." This seems extremely interesting considering there is already evidence pointing towards gdrive.com belonging to google. I can't wait to see this coming!
Google Music / Google Tunes: Following up on an article by forbes, Garett Rogers does some research on the subject, and discovers that a google music player might be available for download soon. Considering the Google Video Player download link from which the information was deduced, in all probability Google Music will soon be available (though the rumor of their buying napster was denied by google...). I can easily imagine free songs from artists on the rise, and a small fee for commercially available songs (or does Google make enough money from ads already? :P)
Google Calendar: By sorting through source code, some curious bloggers have been able to explore pages that were not meant for publication but were available through tweaks of URLs and such. Note that those methods are no longer available, so other than conjectures and the fact that calendar.google.com redirects to google instead of giving an error, there's not much to go about for now.
GMail enhancements: The first of possible enhancements is a Voicemail features, which is given away by the fact that the name "Voicemail" is now forbidden of use as a label on gmail. I noticed about a week ago that my voicemail filter on gmail was not working, and when I tried to recreated it it gave me an error message saying the name could no longer be used... I should have taken more attention to detail, I didn't realize at the time what this meant.
The previousely mentionned Google Calendar could also be integrated into GMail by default, and as you can see from the links, a Google Links service seems to be upcoming.
Google OS: It's logical to think that Google will come up with a centralized solution for all their software and services in the future. Some think it will be a browser, others think it will simply be a software interface. Whatever it is, it's probably going to be dubbed the Google OS by most people. It would provide access to your GDrive, GMail, Bookmarks (cached versions for speed?), your favorite news with the rss reader, and all that crazy useful stuff. Google already registered gbrowser.com, but I wonder if they know that googleos.com is already registered to someone else...
Seriousely, I just can't wait for all of these things to come alive!