Oh Preview!
Having recently made the jump from PC to Mac, the one program I really missed was Picasa (I have parallels and can run it from there - but it takes a while...). I'm sure many know the fab new 'basic' image tools in 10.5 preview - but I've just found them and, well cool! Basic resize, crop and colour adjustments all within preview, a great little time saver. More at: http://www.macworld.com/article/132468/2008/04/workingmac2504.html http://www.macosxtips.co.uk/index_files/13-things-you-didnt-know-about-preview.html
