Places where the game has to reload are great for harvesting and re-harvesting the same items. One of the best places for this is probe room one on the alien spaceship. After rescuing Randy, you may enter and re-enter the room to harvest the many collectable items. Unlike other breakable items such as mugs, brooms, etc., the probe room almost always gives away microchips, glass and goo that you may sell. Ten minutes of spawning will solve most of your in-game cash flow problems.
In the image above, you need to have rescued Randy and have allowed him to run off.
As you can see by the image, there are plenty of things to break and they produce items almost every time.
