What Can Be Done: Baden is a very appealing country to collect as it can be collected as simply or as complexly as a collector might want. There are less than thirty stamps needed for completion, so the appeal of completing a major classic philatelic country drives many collectors to the stamps of Baden. And, Baden is one of the least expensive of the German States to collect and complete either mint or used.
As is true of much of the German area, Baden can be collected at levels varying from elementary to exceedingly complex depending on the interest of the collector. Advanced collectors try to find multiples (pairs, strips, and blocks) and collect the stamps on cover. The Baden postal service used a two tiered cancellation system. The envelope was cancelled with a town cancel from the city where the cover was mailed, and the stamps on the envelope were cancelled with a number inside of a ring. Each town in Baden had a different numeral cancel, and it is a particularly appealing subspecialty of Baden collectors to try to get all of the town numerals on all of the different Baden stamps. This creates thousands of varieties. The Michel stamp catalog prices the different ring numerals (as you would imagine, the ones from larger and more 
commercial towns are more common than those from smaller towns).
Stamp Catalogs: The Scott Classic catalog for Baden is very good. It lists the stamps and makes an attempt to list varieties (and the varieties on Baden are mainly minor shade varieties) and stamps on cover. The Michel Specialized catalog for the German area is a work of art—the collaborative effort of hundreds of the world’s best philatelists spanning, now, almost two centuries. You might want to use Scott, but you should at least look through Michel. It’s written in German, but philatelic German is easy to get comfortable with, and now Google translate makes everything accessible.
Stamp Albums: German philately is dominated by three German album publishers—Lighthouse, Lindner, and Safe. They are all good and all sell their specialty albums as part of their German States series. Lighthouse has more market penetration in the United States than do Lindner and Safe, but all three albums are very good. The Scott Specialty series is also popular.
Availability of Material: Considering that Baden issued its last stamp nearly 150 years ago, philatelic material from this country is surprising plentiful. Again, few of the stamps are individually rare. What many specialists do is buy multiple collection lots of Baden and reassemble their collections by stamp and by issue. That way cancellations, varieties, and shades can be obtained at a relatively low cost.
Expense: There are few rare stamps of Baden, and like most German States, collection lots can be bought for under 20% of catalog. The country can usually be completed by Scott for a few hundred dollars. Even mint, the country is so very affordable (considering the rarity and scarcity of the material) that collectors are usually glad they decided to specialize in Baden.
Overall grade: A-