What Should I Collect Next?

I suggest you change to another hobby. The reason is then there would be more coins out there for me.
You could try Beanie Babies for instance. I hear the prices are really great lately.
For real I collect almost all denominations. I really don't like the Liberty Head Nickels due to for some reason not much value and little interest. Even in MS grades only a few hundred dollars. Shield nickels are OK but really hard to find. Also, very limited amount of dates 1866 to 1883. And the cheapest ones at coin shows go for about $15 in the worst grades.
My vote is for Barber or Liberty Head Dimes. Really easy to find at coin shows, coin stores, internet. Many of the later dates only a few dollars. Naturally like many collections, if you put them in an Album there is a place for dates like the 94S. You won't find many of those anywhere. If you chose that one move fast. Remember the population is growing and more and more coin collectors are poping up every day.

How about 3CN? :)

Relative to most other types, I would say the Peace dollar should be a cinch to complete. That's what I plan on completing next. They're also large in physical size so there's more substance (in the literal sense) to your coin album.

Between Barber dimes and Shield nickels, I like Barber dimes- the design is prettier and it also has the silver content to help keep them valuable. It does have a lot of challenging dates. I only need 7 for the set, all keys, and all too pricy for me to afford. I haven't really started on the Shield nickels in ernest, but I have a few low grade pieces and afew no date culls.

I love the beanie baby idea! My grandmother actually collected them because she thought they would be a good investment. I hope they are not left to me :)

Shield nickels are unique. Barbers (for me, IMHO) can be collected as a type across several denominations and not cost a fortune if you don't need key dates. In that light, you could do both over time.

Thanks guys, I finally have decided on the Beanie Babies, they are much less expensive than coins. I actually ran into a couple Shield nickels for sale tonight and that cemented it for me. Some of those dates will be rough though. They are less popular so I still have a chance at the keys for 1000.00 and under. Thanks again and Prethen, the 3CNs are done, but thanks for the tip.

Oh absolutely, I just try to get one thing out of the way so I do not end up with a bunch of half-filled sets. I plan to at least try everything.