Since you are not always going to have key access to the internet, or it may be limited when you do, you will want to employ the Pin drop feature. What this will allow you to do in your Google Maps section is to set a "pin," which stays in a locaiton on your virtual map, at a location that you will return to.
Start by first searching for an area, allowing it to be found on your map. This is best when used at an exact address rather than a general location. You can also set this for a Current Location, which will allow you to actually just return to the locations you have been to and will allow you to mark one when you are there.
To set the pin you go to the lower right hand corner of the display that looks like a page peeling away and select it, which does actually peel away. From here you will choose to set a pin, or replace a pin if you have already set one. You can do it at the selected location or the current location as has already been determined. You will have to replace a pin if one already exists as you cannot just set multiple pins.
This is an internal function of the iPod Touch itself and does not go to a GPS location directly, which is why it is really only a temporary solution for essentially remembering the searches that you made with the GPS service to begin with.