Macro Lens

[no_steeze]

currently i have no money, but i'd like to brainstorm as to which macro lens i should get. it's my next step in the lens quiver because i just love shooting things up close. i shoot with a canon 40D and my lenses now are a tamron 17-50 f/2.8, a canon 50mm f/1.8 and a canon 70-200 f/4, so i'm looking to fit in a macro lens. I can't spend more than like 500 on this, so any suggestions would be awesome.
i was looking at the canon 65mm macro but i couldn't find anything on it, it doesn't seem like that many people use it. so yeah, i appreciate good lenses so i'm willing to spend some money on it but i can't drop a shit load. i'm also probably looking for something prime, i know there's a sigma 17-80 macro or something but that'll be overlap with my 17-50
or, if some people have used and liked magnifying filters, recommend some as well
thanks

 

[*Fujative*]

I have used the Canon 105mm macro, and that was a lot of fun.
Try this.
Remember that thread I made about making the old Pentax lens fit on my camera? Find an old lens, and flip it. Put the front of your lens at the mount. It will become a macro. Granted there is no auto focus, but its cheap, maybe even free and hella fun.