Must say its Font Explorer Pro (FEP) for me! (MacPro OSX 10.6.8 Indesign Creative Suite 4, Indesign 5.5)
When I first started this job they had suitcase and I found that program really limiting. But I also had never used it before and knew very little about it.
FEP has many things that I like about it.
1. Although most people lean away from font auto activation the one that comes with FEP has been working real smooth, a few second delay when opening files while it starts what font is required.
2. Font Preview is amazing, select the fonts you want to compare with a typeface you have and you have transparent view and slide show.
3. Font Groups: Where you can put all fonts for particular jobs into smart sets.
4. Search files and discover which fonts where used inside that file and save that as a font set
5. There is also a server version of the program.
6. Application Sets: Really handy for auto activating fonts used only in certain programs.
7. Good Conflict control.
The list could possibly go on and on, in other words, love FEP and highly recommend it.