Today I installed one of those RAM expansions for the Amiga 500/1000/2000 made by Kipper2k. I thin they are absolutely great. Not only you get 4 or 8 MB Fast RAM, but you also get a IDE-CF adapter that you can use as a solid state harddisk. You can't recognize your A500 after you installed this. Recommended!
As far as I know Kipper2k is no longer in business. Try AmiBay.