Well DSTT is an excellent cheap solution, got mine for about $25.
Pros: price, excellent game and homebrew compatibility, cheat codes, hot key for in game reset to go back to the menu, moonshell runs fine, comes with rumble pak, EZ flash 3-in-1 works using GBA loader.
Cons: Menu not that pretty, file listing is not sorted by name but by date (there are some workarounds for this), crappy microsd reader included
I ordered an R4 pack with an sd and everything way back in december but after no stock for months decided to use that and get a Supercard DS One which just arrived three days ago and could be the best one.
Pros: everything the DSTT does, plus a better package, a better microsd reader, a great menu, which has moonshell built in so mp3 and txt can be run right there, the files are sorted (tip: hide folders and files you don't want to see), an in game menu to use a game guide (from a converted txt file like a faq you can open it, read it, make bookmark and everything) and the greatest thing ever ............ REAL TIME SAVING!!!!!!!!
Cons: none so far
Maybe R4 or M3 will get RTS setup by next update but so far I've read everywhere Supercard is the first.
http://eng.supercard.cn/manual/dsone/