The reason why InDesign shows up crappy images is because it is a Page Layout application. With this, it takes a low-res thumbnail of the image to show you the image in the layout for position only. The image is linked to the file on disk. So the resolution and quality you see on the screen in photoshop or illustrator is what will be printed.
You can see a higher quality preview of the image by going to View>Display Performance in InDesign
If you need to know how to make high-quality pdfs for printing in lithographic then I recommend you download and read this pdf
If you have cs4 then change the URL to cs4_printguide.html at the end there
Now to clear up some things from Nocandu - for information purposes only.
Jpegs are fine to use. But I wouldn't make edits to a jpeg and then save it as a jpeg again, I'd save it as a TIFF or PSD, but only if making edits.
Opening your JPEGs and saving them all as tiff or other format won't improve the JPEGs.
If you need to resize the images, it's best to do this in Photoshop. Again if you need to open a jpeg to resize it then it's best to save it as a tiff.
There is absolutely no way in this world that I would use PNG for print work. PNG are 24 bit and only support RGB, not CMYK which is needed for print.
300 ppi is a myth also. Typically most RIPs have a lpi of 150.
Since the square root of 2 x lpi = desired dpi is enough to deal with pixels rotated at 45 degrees.
square root of 2 is about 1.5 x 150 (typical lpi of rips) = 225 dpi
Which is the minimum required for lithographical printing.