If you have the .APK files on your SD card (FAT32 partition), you can use a file manager, such as Astro to browse the SD card. When you select the APK file to open it, Astro should launch the Android app installer and give a prompt to install the app. You will need to allow apps from unknown sources, but it will ask you about that the first time you try to install.
If these apps are installed on ext2/ext3 partition from a previous Android phone that used apps2sd, then I don't think they can be browsed from the file manager as it doesn't support these partitions.
