An inexpensive and very competent piece of software is Picture Window Pro ( Digital Light & Color - Picture Window Pro 5.0 ); you can download a 30 day trial version. I used this for several years and found it to be perfectly adequate and much more intuitive to use than Photoshop (not mention being a fraction of the price).
PSE 7 (used most often for touchups and general mucking about)
Lightroom 2 (when cropping and exposure is is all that's needed or when making auto corrections to a batch for simple snapshot prints)
Noiseware (community edition, liked it well enough to order pro edition)
Fastone (rarely)
Silkypix Developer Studio Pro - RAW work & most processing. Before that, it was mainly Pentax Photo Lab 3.
The GIMP (free), Paintshop Pro X, Paint.NET (free) - special editing
XnView (free) - general viewing, copying, resizing - small, portable (USB stick), powerful. Sometimes FastStone (free). Rarely Infraview (free).
Picasa (free) - not for processing, only for organising & uploading to Picasaweb
FDRTools Basic (free) - HDR
Hugin (free) - panaromas
Candidates:
PhotoAcute - Photo stacking for NR or DOF , super resolution.
Noiseware Community Edition (free) - tried this once before, but didn't understand it - when I tried it again a couple of days ago, I was much more impressed.
I currently use PS Elements 6 for Mac (and Bridge CS3 that comes with it) for my RAW files and iPhoto for my JPEGs. I've just begun using Lightroom 3 Beta to see what I'm missing (or will soon be).
I have the choice of using Photoshop, so I use that (not that I'm good with it).
But I always shoot RAW as well and use Adobe's own Camera Raw plugin to process the RAW images.
Yesterday I had the opportunity to meet Photoshop grandmaster Russell Brown and he demonstrated two new experimental new developments that might come to Photoshop. Very exciting stuff...
The first was having an image that can be mapped somewhat like the warp transform tool but with selective control points. So if you shot a photo of someone with their hands up, you can literally move his arms around his body by constraining the transformations.
The second is the ability to be able to pick up colours from and image and blend them for use like an artist brush. One can literally take any photo image and very quickly do an impressionistic or water colour or ink interpretation. No artistic training required. Jaw dropping amazing stuff.
I have used PSP (Jasc / Corel) since V8 ( although I skipped V9) and am now using version X2 Ultimate.
It does everything I need, but note that they (corel) are a little slow to upgrade for newer camera models. It will currently support K20 and earlier models but not K7 yet.
ALso I note that the DNG support is a little flakey, and to insure that it will open either PEF or DNG files I have to use adobe's dng converter first.
Having said that, I shoot mostly JPEG so it is not a big issue,
I've played a bit with iPhoto - thought it was a little heavy handed at times.
I downloaded the trial Aperture when my computer was in the shop - very much liked the program. If I didn't already own Lightroom (been using it since the original beta version), I very well might have chosen it over LR2.
Bought PSE6 for my husband's computer - in the couple of weeks when my computer was in the shop I didn't find anything that I wanted to do that PSE couldn't do. I know CS4 does things that PSE can't, but they aren't things I use on a regular basis. I was really impressed and pleased with it.
I continue to use Lightroom and CS4 - been using Photoshop since PS3 and while I don't make good use of some of the newer features, I understand how the program goes about things and I'm used to it. I have access to the academic discount, so it makes the programs affordable (with the discount Lightroom is cheaper than Aperture).