An image scanner for photo's, text etc? Anywhere from $50-200. Epson, Cannon, HP are all fine.
Keep away from Brother, poor results with low contrast originals like doctors receipts and other carbon copy forms.
If you have a lot of scans to do a scanner with a document feed is a must (and 50% more expensive at least). How many items you are scanning is important for reliability (jamming) and life. If you need one with a document feed then I'd suggest HP. It's what we use at work and I'm always tossing piles of data at it. Fast, no jam, file type/size options in the menu. But... $s.
Combo units (scan, copy, print) may have a quirks like if one ink is out you can't do anything with them (Brother for sure).
Resolution - unless you are ripping commercial photo's and trying to blow them up it's not an issue anymore. They are all ok. You will find that the files are too damn big to store and you have to lossy compress them anyway.
Scanners that say they can handle negatives and slides are not very good you need a dedicated scanner for those $200-300.