G-Mail: Google as started offering its popular e-mail client for use on hosted networks.

Webmail.us:

Sproutit:

Word Processing

Writely: Probably the best online word processor available.

Writeboard: Another quite good online word processor.

Ralleypoint:

Jotspot Live:

Zoho Writer:

Spreadsheet

Numsum: The best online spreadsheet.

EditGrid: Nice-looking spreadsheet — check it out!

iRows: Another excellent online spreadsheet.

Jotspot Tracker: Combines a spreadsheet with a Wiki.

Online Spreadsheet: Ugly, but works

Trim Spreadsheet: All Javascript spreadsheet engine.

Calendar

30 Boxes: Best online calendar software

CalendarHub:

Airset:

Hula:

Joyent:

Kiko:

Planzo:

Spongecell:

Trumba:

Presentation

S5:

SlideML:

Project Management

Basecamp: online project management

SidejobTrack: keep track of your side jobs

Mini-Suites

Zimbra:

gOffice:

Thinkfree:

Groowy:

Online Desktop

Protopage: Simple online desktop

YouOS: Web-based Operating System

eyeOS: Web-based Operating System

Homeportals: Web-based desktop

Miscellaneous

Google Maps: Maps, Directions

gModeler: online UML diagrammer

Painter: online paintbrush

WebNote: Post-It Notes

GChart: Integrated with Google Maps, gives local times, dialing codes, and other information

Flickr: Online photo management

Del.icio.us: Social bookmarking

TagCloud: Social bookmarking

Odeo: Online (”clientless”) Podcasting

Travbuddy: Interesting travel site — reviews and recommendations

Digg: news aggregation

Mooflex: online content management suite (currently pre-beta)

Meebo: online instant messaging (AIM, Yahoo, ICQ, etc)

Rollyo: create a “custom” search engine