Linux has several alternatives for photo handling, IMHO digikam is one of the best.
I agree with your comment about mail software, but there also Kmail.
For user-friendly webdesign there's Nvu/Kompozer (old Mozilla Composer), but that hasn't had much development in years.
For genealogy there's Gramps, but that's a bit more "technical" than most Windows alternatives and I think the other Linux genealogy programs are www-services.
For home accounting there are also several alternatives, but for tax stuff, nothing (at least very user friendly), partly because that is so specific to each country and the taxation rules change every other year.
For CAD there's also QCad (http://www.qcad.org/), but Linux CAD software doesn't really compete with professional Windows versions. (I've also had some problems when exchanging DXF files between Autocad and free version of Qcad, but that was decade ago)