this is going in 'touring' because i see the most gps threads in here. but it should interest any and all flavors of gps bikenerd..
so i bought a gpsr this week. it is so so awesome. the software issues can be a headache, though. and i quickly discovered that making your own custom maps is really really complicated. here is my review of the gps i bought and the results of my several days of obsessive software research:
first, this is a bike forum, so im just gonna say-- get a garmin, no question. next, i highly recommend the etrex venture cx, which is what i bought. its not a 'cycling-specific' unit, but i want it for other things than biking, too. the 'cx' means it is mappable and takes microsd cards. dont even bother with a device that cant do this. i paid $190US for it. if you live in europe, find a usa friend to send you one (thats what i did), cuz its like 3x cheaper over there.
the venture is the cheapest one in the new etrex cx line, but the other models are virtually identical for a HUGE price increase. do you have a usb cable like the one that came with your digi camera? good. do you not mind carrying a cheap compass 'just in case'.. or just not worrying about it? good. are providing these two things worth $50-150 more? ummm.. *cough* you, garmin.
ok now some comments on software.
1) do not underestimate garmin mapsource! i did at first, because it is hugely expensive and very difficult to pirate. but after tooo loong looking at other applications i finally came back to it. it is rad. it even has some miniscule mtb trails running through the black forest in southern germany. and so far, its been dead-on accurate. also, the only difference between the pricier 'city navigator' and the lesser 'metroguide' is that the latter is not routable. but there is a freeware hack to fix this. get it here.
2) google earth. it might seem to be little more than a bloated version of google maps. and this WAS my opinion until i found a program called stitchmaps. it may not be worth the cost, but with this program you can compile a single jpg made out of hundreds of google earth images (taken at the closest level, with the most detail) for basically as large a region as you want. and it does it automatically in just a few mouse clicks, including automatically calibrating the whole image. i now have the whole of southern germany in a huge jpg ready to be plugged into mapping software and exported to my gps unit. i think thats just great.
3) easygps (freeware) and expertgps (shareware version). decent editing software if you cant get yourself a copy of the more badassed..
4) global mapper! this is what im using now, and it just kills it! automatically fetches usgs maps (including topo). and if your area isnt covered, you can import maps (like from stitchmaps). if they are not calibrated, it makes it relatively easy (calibration is a total headache.. thats why stitchmaps is huge).
5) using the map editing programs you need to eventually get from raster images (photos, scanned maps, etc) and other data input (topographical info, etc) to a vector image (line and point based image). and specifically in the '.mp' file format. global mapper, for example, has a simple 'export' command that can compile your image data and save it as an '.mp' file. once you have an '.mp' file, you need to make yet another conversion, since garmin has chosen to be a ***** and use a proprietary format called '.img'. the only conversion software that will build you an 'img' file is cgpsmapper. luckily its free to use. only catch is it runs as a cmd prompt, which can be awkward for some people (but see #6, if this is you) the same author has also developed a great piece of software called 'sendmap', which allows the easy transfer of map files to your gpsr (same download link, scroll down a bit.. its also free).
6) the last program is gpsmapedit. its shareware, but theres a free version with most functions. this one does similar things to global mapper and expertgps but with a few hidden tricks that make it worthwhile. one of them is that it integrates cgpsmapper, so you can convert from .mp-->.img from within the mapedit file menu.. which makes that step a bit more convenient.