Sibelius of course



...which also include the tone poems, quite wonderful at mid-price. Alternatively the Osmo Vänskä / Lahti orchestra set on BIS is quite good, again, the last in the series (I believe there's a complete boxed set available, or you can purchase the individual discs) including symphonies 6 & 7 & Tapiola takes the proverbial bis-quit.

Rather good are also the Sibelius string quartets, I particularly like this Ondine recording of "Vocess Intimae" (by the appropriately named Jean Sibelius Quartet)

Then something a bit more modern, but fascinating - Einojuhani Rautavaara; I'm new to his music but just lately have been listening a lot to the "Unknown Heavens" Quintet (also on Ondine):

I'm tempted to try his symphonies as well, this quintet was such a pleasant surprise to me.
Hmm... maybe that's it, not that I'm an expert on Finnish classical music anyway (actually I have far more music by British composers

A good general resource for info on Finnish music is FIMIC's page: http://www.fimic.fi/
Any other recommendations...?