Is there an alternative to iPhoto on a mac?

I don't have personal experience with it, but Adobe Lightroom might be what you're looking for.

I should also mention apple's entry, Aperture (http://www.apple.com/aperture/), and a smaller, much less expensive option: Lightbox. http://www.lightboxsoftware.com/

Photo Mechanic (http://www.camerabits.com/pages/PM4.html)

I personally use Aperture, and I *love* it - but it may be way too advanced for your needs. I've never used it, but I've heard of Picassa, I think google owns it or something. You may want to look at it. Why are you looking for an alternative?

I hate iphoto's organization system, and it runs slow and crashes a lot. Also, sometimes it spontaneously downsizes and "loses" my photos. It's kind of a huge problem. Free suggestions are much more convenient, but thanks for all the helo everyone.

I've actually heard of people running Picassa in Parallels just to avoid iPhoto. That said, Aperture or Lightroom or Bridge will probably do well. If you're going for not as heavy weight, Photoshop Elements has an excellent organizer (including a really strong tagging system with a facial recognition thing-- it'll find all the faces in your photos so you can tag them with the names of the people...)

it really depends on what you're trying to do.. and what you're priorities are. If it's mostly about organization - Picassa2 is great. It'll also do a fair about of editing, on a simple level. that said.. my first thought when I saw this question was Photoshop Elements - i doubt you really need to invest in buying the full Photoshop, and Elements would probably be a superior option for what you're looking for. the toss-up of course is that Picassa2 is free, whereas Elements costs money. :)

Aperture and Bridge user here. I like the both for different needs.

I haven't used Aperture yet, but hear it's wonderful. I have a simple folder system and use Bridge to view and sort. Easy enough! iPhoto also strips information from dig photos--not what you want to have happen!