I previously had a Garmin Forerunner 201 watch which allowed me to see my pace and distance on the run or on skis. I managed to lose it after a 50K ski race but hesitated to buy another 201 due to its performance under tree cover
I found that on our New England forested trails if there was leaf/tree cover I would often lose the signal with the 201 . So I was very interested to hear the claim the new Forerunner 205 and Forerunner 305's (inlcudes heart rate monitor) had, along with a more watch like form factor has much improved reception under tree cover. An excellent blog by John Sun has an extensive series of superb comparative trail runs . Using some of the Google Maps based sites listed below he plots the performance and accuracy/wanderings of the 201 and 205 side by side on maps. John was able to convince me that the 205 is a significant improvement over the 201.
Several sites such as MotionBased (owned by Garmin), Sportstracks, Bones in Motion allow users to upload GPS data from GPS units, from certain Sprint and Nextel phones via a subscription from Bones in Motion, or to manually click out and measure your route via overlays to Google Maps. As previously discussed in one of my other posts all of these solutions use "mash ups" Google Maps.