great choice of collecting area, i must say.
current issue world notes are easy to find, relatively cheap, and they make for an extremely enjoyable hobby! there's plenty of different colors, sizes, materials, histories, languages, cultures, and other reasons to stay hooked. it's always interesting to find out what people and places other countries find important enough to put on their money. there's many different ways to go about collecting your notes, and i'm sure you'll learn plenty in the days to come. the hunt is part of the fun! what countries do you consider obscure?
does condition matter for you? if it doesn't, the easiest place to find circulated notes are at money changers. most airport currency booths will charge a nominal fee of $5, but the rest is face value. hotels are even better. the front desk will exchange your money for free if you're a guest. otherwise, follow see323's advice. most coin shops have loads of world currency they throw in "junk boxes". the last coin shop i went to had a box full of bills selling for 50 cents per note. most coin dealers don't have the time or interest to catalog circulated world currency, (unless they know it's rare), so they just lump them all together and try to get rid of it.
if condition does matter to you, the internet is full of world note dealers that sell uncirculated notes. the only drawback going this route is cost. the going rate for uncirculated notes is around twice face value. unless you go on vacation yourself or have friends that can check different countries for you, that's what you're looking at. the good news is that coinpeople is international, and we have members living all over the world. i remember one of our members vacationed in estonia and was able to pick up a few new notes directly from the central bank. but his next vacation was in sweden, and perfectly uncirculated notes were a little harder to track down.
anyway, have fun on your new hobby, and welcome to coin people!
p.s. - here's a good reference site that lists most of the world's currency:
Ron Wise's World Paper Money.
i think the concensus was that it's a good place to figure out which notes to hunt for next.