"Meine besten Freunde!"

[walty]

Freunde? Why not Freunden??

[Hohenems]

The plural is Freunde.
If they were all female it would be "Freundinnen" (singular is Freundin)

[greenfire315]

why besten?

[thiagoleal]

I'd like to know too!

[Hohenems]

Plural "ein" word, nominative, weak inflection
http://en.wikipedia.org/wiki/German_declension#Mixed_inflection.5B6.5D

[greenfire315]

It would be "beste" for a "der" word though right?

[Hohenems]

Definite article - "der" word:

• The best friends
• Die besten Freunde
• Weak inflection - nominative - plural
• http://en.wikipedia.org/wiki/German_declension#Weak_inflection.5B6.5D.5B7.5D

No article:

• Best friends
• Beste Freunde
• Strong inflection - nominative plural
• http://en.wikipedia.org/wiki/German_declension#Strong_inflection.5B6.5D.5B7.5D

[az_p]

For a singular "friend", yes:

Der beste Freund
Die beste Freundin

But for ein-words, you need to inflect it differently:

Mein bester Freund
Meine beste Freundin