I've found the safest toys are the ones I make. I crochet, so there's an endless array of things I can make for him. Little balls, fake mice, "snakes", etc. As long as the yarn is secure (and you keep an eye on it, as ANY toy can be rendered unsafe if pieces break off and they eat it), I've provided many hours of fun for very little time and money. (If anyone wants a few crochet patterns, PM me.. I can also find some knit ones for ya.)
Since I'm a total craft maven, I also make my own plush sewn toys, feather toys, string toys/lures, and I grow my own catnip. I find it ridiculous how some major pet store chains overcharge for the simplest of toys. Plastic grocery bags can be a blast, albeit simple.. I just cut the handles and make sure there are holes in the bag in the off change he gets stuck in it. The ones ya get from the liquor store (hehe), the heavy duty black ones, are best 'cause they don't rip very easily.
I will say, though, the only toy I have bought and felt it was worth it was Da Bird. they sell replaceable attachments, but I think with all the feathers I have (and they're real and un-dyed, not those stiff neon fakies) I think I can make my own replacements when he eventually tears this one apart. That toy is /excellent/ and is the only one I don't have to rotate 'cause he never gets bored of it.