The GetSETWomen Blog is a great source of inspiring women in technology to blog about for Ada Lovelace Day.
The UKRC's GetSETWomen network for women in science, engineering or technology (SET) site also includes an astronomy blog where a variety of women will post 'a one-off entry about the role of astronomy and outer space in their lives' for the International Year of Astronomy, and the 2008 Outstanding Women in SET: Photographic Exhibition is another good source. It's a shame they haven't listed the 'outstanding women in SET' for 2009 ahead of the launch of the exhibition but check back in mid-March.
[Updated to add:] The Global Women Inventors & Innovators Network(GWIIN) website might also throw up some leads, and the related British Female Inventor of the Year award site has some great stories about women inventors.
I've also been listing inspiring women at modernbluestocking.freebase.com, though as it's a much broader project, not everyone listed works with technology.
If you're not sure why female role models matter, these articles explain it well.