[tbob]

Scott- certain pre-war minor league sets have experienced a marked rise in prices over the past few years, although lately the economy seems to have tempered things a bit. The early Zeenut sets went through a flurry of activity and dramatic rise in prices but have leveld off a bit in the last 6 months. 1911s and 1912s in particular had been pretty hot. The Obak cards from 1909, 1910 and 1911 featuring PCL an NWL players have shown a marked increase in price but I think a lot of this was because collectors had finished basic pre-war major league sets and wanted to move to other sets and the Obaks are beautiful and have long been underrated and underpriced.
The economy seems to be leveling off a lot of the prices lately and now is a good time to buy. Pacific Coast Biscuit cards are much more reasonable than 1 year ago and the D311s are very colorful and desirable.
In my mind the most stable set of the pre-war minor league issues, as far as growth and prices, has been the T210 set. After an inital spurt, they seem to be available at a good price now, even the tougher Series 4,6,7 and 8 cards. Some collectors don't like the lack of color (only the red borders) but these Old Mills are very nice, especially in nice condition.
Other sets such as the E99s, E100s, etc. have dipped a little in price although they are still very sought after and are still pricey compared to the others I have mentioned.
If I were going after pre-war minor league cards right now, I would be buying up Obaks and T210s. Try finding them in lots in you can, either on ebay or in auctions. Several collectors I know collect the T210s by teams (towns).
Good luck!
tbob