Hmm, how about some Illithaid Savant Love.
Illithaid Savant 15/Factotum 5//
Factotum 1/Telepath 1/Factotum 1/Telepath 1/Factotum 1/Thrallherd 2/Illithaid Savant 10/ Thrallherd 3
Go with the Psioinic Version of the Illithaid and assume the manifester level is HD+1. Take telepath early on non-HD levels to advance telepathy further. The key creature to eat is a level 10 Legacy Champion. Use the Legacy Champion to advance your classes by 8 levels, you can raise and repeat as needed. Assuming you just eat that class feature twice, you could push Thrallherd to level 10 and Factotum to level 19, and still have room for another class ability. Plus you have access to thralls for psionic surgery to pick up more powers with your telepath manifesting. If you have trouble getting ahold of a Legacy Champion, only put 3 levels in Illithaid Savant and push Thrallherd to the point that you can get a decent level Legacy Champion as a Thrall. If you are not into Factotum 19, you could always through in another PrC and advance that to the max level with the champion eating, or only eat one legacy champion.
The ethergaunt build mentioned earlier is fun. I like:
ethergaunt 20//Factotum 8/ Eldrich Master 10/Monk 2
Monk can be used to get evasion and Int to AC with the proper feats. Eldrich Master at level 4 and 8 will grant another spell casters list to your own. So you can roll with Wizard, cleric, and another of choice off of your ethergaunt racial spell casting. I similarily like:
Beguiler 20//Bard 1/Cleric 1/ Spell Theif 1/ Marshal 1/ Wizard 1/ Eldrich Master 4/ Dweomer Keeper 1/ Sublime Chord 1/ Dweomer Keeper 9
Add cleric spell casting to your Beguiler and all your other classes because Eldrich Master does not say just one class. On the other side you have cleric, sorc, and bard spell casting. Master spell theif feat tricks can also be added in to get a caster level of ... Really high. Sublime chord caster level of beguiler +10 sets every class at a caster level of 30, X5 puts that at 150.