Some 7805 like : 78M05CT or L7805CT are the same in Voltage but not Current. Some are max 500 mA, some higher like 1 A or 1.5 A. Just do a search at http://www.datasheetcatalog.com/ and type the part number to download the datasheet. When a regulator goes behound the current rating, the regulator shut-down temporary, so make sure you know the total current being use and having a heatsink will help a lot, because when it is too hot, it will shut down.
Something to bear in mind about regulators.