Aside from Microsoft Powerpoint, can anyone recommend any programs/software to make effective and attractive presentations? Preferably on a PC.

Take a look at Prezi.com. A very different way of presenting, but sure to catch our audience's attention. Small learning curve, but easy to make snappy presentations quite quickly. Also allows for straying from the usual PPT linear approach, i.e jumping to different parts of the presentation as needed.

(Disclosure: no relationship to Prezi.com, other than an occasional user)

I second the the Prezi.com recommendation. The only downside to Prezi is that it is done in Flash and so won't work on my iPad.

OpenOffice (www.openoffice.org) is a free open-source office clone that contains a module called "presentation" that is somewhat compatible with PowerPoint.

Thanks a lot for the responses. Really appreciate it!

I came here to post about Prezi too. I have played with it many times though never actually used it in a presentation, I guess I am just not quite that artistic/want to take the time to make it work/look good.

To the OP are you trying to make presentations more flashy/pretty or do you just not want to buy Office? I still think PowerPoint is the best at what it does and if you really know how to use it and avoid the templates they give you, it is surprisingly powerful.

Another option, although rather plain (yet free), is Google Docs.

openoffice "impress". free and essentially does everything powerpoint does. openoffice is a suite so there is also "writer" which is a word-processor, a "calc" which is a spreadsheet etc.
http://www.openoffice.org/

Not that I want to make them "flashy/pretty", just finished school, spent the last 4 years doing nothing but powerpoints and was looking for something a little less boring and more effective.

By "preferably," I assume you mean that other platforms might be OK too; otherwise, you would have written "For a PC" or some such.

If you'd consider a Mac, take a look at Keynote.

I use Beamer for all my presentations. http://en.wikipedia.org/wiki/Beamer_(LaTeX)

Slide Rocket is very impressive. They have a free light version and a pay-for full version at $24/month or $240/year. Also if you have a Mac or iPad Keynote is also impressive. Keynote is part of iWork which is going to be upgraded in the next week or so.

Keynote looks neast and clean, as expected from an Apple product, but for some reason the file sizes end up HUGE fo a reason I haven't figured out yet (havent played with it much yet).

As some have stated if you want a free PowerPoint replacement look to Open Office. You can take PowerPoint presentations as input or even output in PPT format. When converting a PPT pay close attention to the fonts even font size sometimes it makes mistakes in this area.
As to making presentations more interesting in my opinion that is the job of the presenter. No matter how many bells and whistles or animations transitions you use, it will make no difference if you do not present the material well.
Another thing to watch out for is if you work for a company that has Branding police make sure your software is compatible with their Master. In many organizations there is a mandate to the background of slides (think corporate color) and possible the layout at the top (maybe the company logo). All of this must be able to transition to your new approach.
And one last thing make sure you can deliver a electronic copy that whoever you just presented to can open, we usually create a PDF version since our slides have notes.

Google Docs Presentations is indeed capable of some pretty amazing stuff [very entertaining brief video from DemoSlam]

(Disclaimer: I work for Google, but in Geo, not anything to do with Docs)

They include the full size versions of all the media you add. Photos, movies, etc even if you only include a cropped version or short clip.

If you go to the Help Menu and pull up the article "Reducing the Size of Media Files", you'll get a good explanation of how this works, how to use the File Menu's "Reduce File Size" option and the tradeoffs involved.