For VNC-style full desktop access, Teamviewer just works...it runs on Windows and Linux, is very fast, and (usually) doesn't need any special firewall/NAT rules set up. I believe on Windows at least, it can be used to establish a VPN as well.
Might be overkill if you just need to reach one particular service (e.g. HTTP(S)) though, in which case you could consider setting up a reverse proxy (e.g. using nginx) on a DMZ'd server?
Is remote access by TeamViewer established through the VNC protocol? I use RealVNC when I want to remotely control my computer but it's not as fast as I'd like in most cases. Also I'd prefer it if the connection between me and the server I'm connecting to was direct and wasn't being routed through the servers of a third party. I checked Wikipedia and it says direct P2P connections happen 70% of the time but I'm not so sure.
Might be overkill if you just need to reach one particular service (e.g. HTTP(S)) though, in which case you could consider setting up a reverse proxy (e.g. using nginx) on a DMZ'd server?