It depends what you want to do with the scans.
For commercial work you will need to do TIFFs at 300dpi and look at the output dimensions - for example, 30 x 40 cm or about A3 size - but remember the file are big, like 40 - 50 MB
For home use - maybe making decent prints for family and friends, you should find JPEGs more than good enough. 150dpi and max 20 x 30 cm or A4 and no bigger than 5 MB
You may want to convert your files to emailable size as well - 150kb or so
I donÂ´t think you should worry about complicating the issue unless you are into serious commercial stuff. Then youÂ´ll really open a can of worms including color management issues.
I use the basic version of Photoshop, called Elements v. 3 - Adobe have recently released v4 which should be more than enough. There are plenty of alternatives however. One freebie that is very useful is Irfan View - it allows you to do very fast conversions to other formats, sizes, etc.
NOTE: Keep your scanner clean - itÂ´ll save loads of time later, and your eyes (IÂ´ve spent up to 12 hours cleaning single images because I couldnÂ´t get the original neg to scan!)
Have fun with your gun.