Though I'm an avid fan of Linux at home and on my laptop, during the 8-5 I'm a Microsoft Database Admin. There's just something about databases that fascinates me, and with Microsoft SQL Server I have a chance to really get under the hood with CLR's, SSIS, SSAS (still learning this), and the other many tools Microsoft offers.
... And Outside of Work
Using Linux and OSX at home my database of choice on those platforms is MySQL, which I guess I have to say Oracle MySQL now (o_O). I don't use MySQL as much as I'd like, but I'm slowly nearing the in's and out's of this wonderful database server.
Outside of RDBS I'm starting to learn the Object DB model with Apache CouchDB and Amazon SimpleDB, though I've yet to work with any projects that use this type of database. The concept fascinates the heck out of me, so I'll probably start learning them as soon as I can.
My future goals though are to start learning more about Data Warehousing, and the Ralph Kimball books are amazing in this area. I haven't had time at my 8-5 to start putting together a Data Warehouse, but I'd like to whenever possible.