I use a few differing methods but normally it is HF
a) i can use YAAC (Yet Another APRS Client) on my normal PC with "DireWolf" PC TNC, and a cheap VHF radio as described in the original post here to get onto VHF (YAAC can also connect directly to the APRS.IS backbone by internet, but where is the challenge in that LOL!)
b) my most common method is to run PSKmail ( http://pskmail.org/) and FLDigi in my "radio" computer connected to my FT450D on 10.147Mhz and beacon from there . PSKMail also can be used as an HF to internet mail system, but there are not enough servers, so can be a challenge!
c) I have experimented with "old fashioned" AX-25 unproto packets on HF ( normally 10.14760 USB DIAL freq) at 300 baud using CCW Messenger (http://www.crosscountrywireless.net/aprs_messenger.htm) and the UZ7HO Soundmodem (details of how to set this up to work are here http://wa8lmf.net/APRS_PSK63/DualMode.htm ) that works OK but the problem with AX-25 300 baud is that there is NO forward error correction ( FEC) so the entire packet must be perfectly received or nothing The difference here is that on AX-25 there are LOTS of stations listening too, so it is more likely to be picked up and sent to the APRS.IS internet backbone, that is because the robust packet network is there are well, and the legacy AX-25 is often configured in the servers too! - Swings & round-abouts!
d) Recently I tried YACC on HF with the UZ7HO Soundmodem , to see if I could map the packets I received ( it worked!) and then I have also replaced the UZ7HO Soundmodem with DireWolf (with a 300baud configuration). It beacons well and seems to decode the RX packets well too.
You may note that I completely avoid "proprietary" systems like "robust packet"... That is a deliberate decision.
Have a play, I have enjoyed making things work, even if only one out of a whole day's beaconing on HF get there, I feel I have "made" it. Remember we are waaaaay down in the Solar Cycle, so unless the receiving server is pretty close it will be a challenge to get complex digital data through on HF (without resorting to commercial software and Kilowatt transmitters
here is a screenshot of PSKMail receiving the response to a ping on 10.147Mkhz just so this post is not ALL writing