Software development company Synovel is working on a Thunderbird code-base email client with the look and feel of Microsoft's Outlook named Spicebird. The software is currently in Alpha (v .4 coming soon), but several screen shots and feature lists are presently available from the company website.
The software package intends to have Thunderbird email handling with Lightning calendar extensions included to handle scheduling requirements. As a bonus, Jabber functionality will be included, which will allow the user to share and subscribe to web-based iCal calendars.
Also planned for inclusion is RSS subscription functionality, as well as a blog posting client. To take a gander at what they have in store for the initial release, check out Synovel's web demo.