How to create a high res photo collage for publication?

Download http://www.scribus.net/canvas/Scribus, a free page layout problem and do it in there. Save it as a PDF, so people can download, while providing a low res 72dpi to visually display what the collage looks like. http://www.gimp.org/ is another choice, a free program similar to Photoshop. It has layout capabilities, but type usually looks better from a page layout app. However, I am concerned that it is not a very good quality (it does not look good on the screen). Screen resolution is lower than print. Go ahead and print out the slide to get a better idea of what it looks like. Uploading the 300dpi file for people in this thread to look at or print would be helpful, to see if its going to be ok for publication.

This is the kind of thing I will use Photoshop for. It's not cheap and it has a serious learning curve, though. I noticed that Googling on 'photo collage' brings up a smattering of free online 'collage makers'. If they don't handle text, you could first generate the collage and then use http://www.irfanview.com/ to add text (I'm assuming you're on Windows). There are likely other text overlay programs out there, too. All that said, you say you have it at 300dpi but it doesn't look good on the screen? Are you viewing the image at 100% size? Note that if your image is (say) 3000 pixels by 2000 pixels and your computer screen is 1024 x 768, and your software is allowing you to see the entire collage, then it has been scaled downward to fit, and noise may have been introduced. If you display your image at 100%, you'll have to scroll around it to view it, but it might be of sufficient quality.

http://www.getloupe.com/

If you have a 72dpi image and you change it to 300dpi, it won't be magically higher resolution. You need to make it at 300dpi to start with, or have a 72dpi file that is four times larger in physical dimensions than the size you eventually want to print at. PowerPoint isn't great for this but if you have to use it, best thing would be to choose the largest slide size you can (rather than default slideshow size) and save as pdf not jpg.

Argh sorry I didn't see you had changed setting to save at 300dpi! I did not know you could even do that :-\

JPEG is lousy for this. You will likely see fuzz around the edge of the text boxes and the text. Also when designing for print, you really are best off going with a resolution higher than 300 DPI so you don't have to antialias your text, and then don't antialias your text. Because the grey fuzz will be dithered or halftoned into jaggedy edges, instead of smoothing it out.