In case you haven’t heard, a developer by the name of szczuru_pasja has released a program called PSP2PS3 v1.7.3. As the name implies, this program essentially uses a series of tools that allow you to take your PSP games from ISOs and convert them into PKGs that can be played on your trusty modded PS3. Basically what you would do is run ISO2EBOOT first to convert the game then you would sign the eboot if need be and run the EXTRACT_PKG. To end it, you would use MAKE_EDATS and finally MAKE_PACKAGE to produce the final product. It sounds difficult, but as usual I have more info at the source link for more steps.
If that’s not enough for you, the Italian developer Francesco Lanzillotta has gone ahead to make a GUI called Bite 1.2 that will break the entire thing down into three clicks of a mouse using the convert, create, and build steps. It should be noted that the program is indeed in Italian, but by taking a look at the source program images, anybody should be able to figure it out. Both programs are available for download below and they will work independently. DEX users may have a few more steps to add, but in general both of these apps are great to try out some PSP games.